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

Now footprints, after loaded by reading a netlist are grouped by sheets by the footprints spread function, and the grouping is better.
Rename 2 files. Fix minor issues. Clean code

   comment for GITHUB_PLUGIN which should flow into Doxygen output.
*) Rewrote: 
        PCB_BASE_FRAME::Save_Module_In_Library(): now uses fp-lib-table and PROPERTIES.  
        PCB_EDIT_FRAME::ArchiveModulesOnBoard(): now can archive to any writable library type.
        PCB_BASE_FRAME::SelectLibrary(): is now generic for selecting a library, not just the active library.

template: add file fp-lib-table.for-eagle

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.

Pcbnew: Fix a crash on exit when an item was previously deleted. Fix not working footprint exchange functions

FIX: unique renaming of eagle footprints by substituting illegal : and / with URL encoding technique.
ADD: window resize border to DisplayError() windows.

* Make spacing between controls and dialog frame consistent.
* Use default size to allow wxWigdets to determine optimal dialog size.
* Set OK button as default so return key works properly.

* Use std::swap for PCB_LINE_T items in SwapData().
* Use std::swap for PCB_MODULE_EDGE_T items in SwapData().
* Add assignment operator to EDGE_MODULE object.
* Move code from copy method to assignment operator.
* Minor coding policy fixes.

*) Save library nickname in APP so upon module editor re-entry last is re-used.
*) Fix bug editing fp-lib-table Description field.

Code cleanup: remove m_Son member in EDA_ITEM which was never used.

Show the "Description" field from fp-lib-table in pcbnew's module editor 'set current library' dialog.

Fix a very minor bug (2 duplicate lines when copying version informations to the clipboard)

columns.  DIALOG_SHIM would resize each separate usage to the same
size.  DIALOG_SHIM now supports and alternate m_hash_key in lieu
of the class name, optionally.