* Remove redundant definition of KICAD_DATA_PATH since DEFAULT_INSTALL_PATH
  was already defined.
* Use DEFAULT_INSTALL_PATH as the substitution for the default environment
  variable paths.
* Add option to define DEFAULT_INSTALL_PATH during CMake configuration with
  fall back to CMAKE_INSTALL_PREFIX if not not defined.
* Developer note: this change is primarily for package builders where
  CMAKE_INSTALL_PATH is the path where the package builder temporarily
  installs the build output before creating the package.  When building
  packages, DEFAULT_INSTALL_PATH should be set to the path where the
  package will be installed by default.

Eeschema: extend max number of units per package to 52 and clean code to easily extend this value upto 26x26  (but 52 is a reasonable max value).
Fix a few minor coverity warnings.
Add about_dialog typo fix from Nick Østergaard

Fix minor 3D viewer issues (includling change number of segments and its optimization to draw pad holes.)
Fix Bug #1439132 (track and via list on toolbar not always refresh after loading a board).
Remove useless tool in Modedit.

* Fix bug (and Coverity error) when deleting environment variable map entries.
* Remove debug logging code inadvertently left over from development.

* Create new dialog to edit environment variables.
* Add helper class ENV_VAR_ITEM to manage environment variable values and
  if they were defined externally.
* A path configuration dialog access to KiCad, CvPcb, Pcbnew, and Footprint Editor
  window menus.
* Add validator for environment variables.

Better error messge when a .kiface file ( or,  if it exists, a .dll or .so shared library ) is not found at start up

Pcbnew: Force visibility of items which have no option in dialogs to controle this visibility, when reading the .kicad_brd file.
these options are used in GAL mode, but the usercannot control this visibility. So if the board file does not have these visibility flags set, the GAL never show them.
Fix also a compil warning.

Make hotkey string info translatable in dialogs. These strings are now prefixed by _HKI , which can be used by translation tools to extract them.

Fix Bug #1426675 (Undo and cancel commands don't have effect for Duplicate operation in legacy mode)

Plot pdf: fix issue when a 0 sized text is plotted (files are broken): now 0 sized texts are ignored.
pcbnew: remove a false error message when undoing a change on a text, or some other board items (graphic items for instance)

Try to fix Bug #1431391 (Unable to edit pins in Schematic library editor). It happens on XFCE, but also on Unity. This fix works on Unity. (it is due to the fact the dialog is not raised, for an unknown reason, and this bug depend on the way Eeschema and Libedit are run).
Add Ctrl+E hotkey in eeschema to edit a component with Libedit (similar to pcbnew Ctrl+E hotkey)
As usual, fix a few minor coverity warnings

Remove a few coverity warnings. Fix some comments which were incorrect, due to the changes in code. Remove not compiled code (kept as comments), now outdated or useless
legacy plugin: better compatibility with old brd files (current track width and current vias size, stored in SETUP section, were not read from file and incorrectly set)

class PLOTTER: dash lines parameters in one place for plot. I made minor changes (values in mm and set to give the same size as dashed lines drawn by wxDC, using short dash.)

Eeschema now uses dashed lines for graphic lines (to be consistent with plot functions and toolbal icon).
Fix an old bug in some envionments which warp the mouse on a bad monitor when opening eeschema, pcbnew and some other windows, only noticeable guys who are lucky enough to have more than one monitor.

 - CACHED_CONTAINER::GetVertices: removed useless and unused function
   which does nothing but tainted the API
 - SHAPE_LINE_CHAIN::Collide( const BOX2I& aBox, int aClearance ):
   removed an outdated function with assert(false)
 - SHAPE::BBox(): fix a small typo in the doc string

Minot fixes: Minor coding style issues fix (tab -> spaces). Add missing GetClass to all classes derived from EDA_ITEM. Make debug method Show() only compiled in debug mode.

Minor fixes: coding style in 3d-viewer and minor code cleanup, and some fixes in bom python scripts, which did not work when a non ascii char (but a valid utf8 symbol) was found in xml netlist. Add comments.