Minor change: Eeschema+Pcbnew: display timestamp in edit dialogs (for footprints, sheets, components)

eeschema/dialogs/dialog_lib_new_component.cpp was not expanding part name field nor setting initial focus.

Better GITHUB class header documentation, better eeschema library field dialog stretching and title.

Pcbnew: Code cleaning and bug fix in autoplace functions
Dialog exchange footprints has now a separate button to update the .cmp file, only on request.

* Replace all occurrences of the word "part" with "unit" when referring to
  multiple unit components for improved consistency.
* Replace "shared by" with "common to" when referring to objects (lines, arcs,
  pins, etc.) that are common to all units.
* Improve wording in library component properties dialog.

Pcbnew: Fix incorrect bounding box calculation of texts. Only noticeable with boards conveted from Eagle, which are using other text justification than center.
Eagle plugin: filter and replace not allowed chars in FPID(-':' and '/')  by _ or -, if they are used in Eagle footprint names (otherwise, boards converted and saved under kicad_pcb format are not readable by Pcbnew).

* Fix replace bug to handle case sensitivity properly.
* Fix replace bug where the item index was getting updated incorrectly.
* Fix replace infinite loop bug on replace all.
* Make find/replace view update code a separate function.
* Rearrange find/replace trace string to add tracing to EDA_ITEM::Replace().
* Add IsComplexHierarchy method to SCH_SHEET_LIST for future find/replace
  improvements.

* Create a generic yes/no/cancel dialog from DIALOG_EXIT.
* Make DIALOG_EXIT return wxID_YES instead of wxID_OK so it is consistent
  with the standard message dialogs.
* Add missing license to confirm.h and confirm.cpp.
* Change Eeschema message dialog when loading a schematic if the current
  schematic is modified to be more consistent with the exit dialog.
* Change Pcbnew message dialog when loading a board if the current board
  is modified to be more consistent with the exit dialog.
* Remove some Eeschema block debug logging code left over from my last
  commit.

* Merge HandleBlockEnd() and HandleBlockEndByPopUp() into as single block
  end function HandleBlockEnd().
* Replace all instances of HandleBlockEndByPopUp() with HandleBlockEnd().
* Change block hot keys to send command events instead of directly calling
  end block handler.

Pcbnew: Fix issue when displaying net names and/or pad numbers including the "<" char in drc dialog, because drc dialog uses an wxHtmlWindow to display drc messages, and the "<" char has a special meaning and is not allowed in texts (now replaced by the" &lt;" sequence in messages displayed in html)
Eeschema: replace "<" and ">" by "(" and ")" in autogenerated net names, to avoid other issues in html messages.
Very minor other fixes.

Remove wxUSE_UNICODE definition from CMakeLists.txt, because this define comes from wxWidgets and should not be made inside kicad
Remove KICAD_GOST option because it is  now useless: the 2 GOST options are now selectable at run time and are:
* specific page layouts (now user definable, and the GOST page layouts are available in template folder)
* notation for multiple parts per package (made in eeschema, preference menu)

Eeschema: better name for m_SheetList (changed to m_SheetPath) member of  class NETLIST_OBJECT.

Eeschema: netlist generation: fix bad choice for the "best net name" when selecting a net name between labels connected to the same net.
Code cleanup and remove unused file.

Fix an annoying issue about not named nets:
now, these nets are named from the component references and pin names which are connected.
therefore, unless the net or the footprint references are modified, the net name is not modified between 2 netlist calculations.

Pcbnew: better test for allowed layers when creating/editing Dimensions and some other Graphic items
Drc: fix comments and messages for some drc tests.
To do: fix issues in active layer selection when creating a track and layer pair selection dialog

Add <aliases> and <alias> to generic netlist XML format, required by new bom_csv_grouped_by_value.py support.

* Fix Bug 1219239 - EESCHEMA crashes when editing a template field in libedit through the context menu

Lay basis for a more full featured usage of boost, including compiled libraries such as unit_test_framework, system, etc.  Move headers now into boost_root/include/boost/.

* Fix the last parts of Bug 1204712 by removing DateAndTime from library file and documentation file formats. They weren't being loaded anyway.

* Use a regular expression to enforce more stringent bus label testing.
* Add validator to edit label dialog to prevent space character from being
  used in labels.

dialogs which allow editing of component properties.  The button
is active when the table row cursor is on the DATASHEET field only.
When active, and your datasheet is a URI, then your default
browser will be launced to show that datasheet if it can find it.
This incentivizes use of http:// links for datasheets.