minor cleanup. minor enhancements. Finish file housekeeping. add Bug 682586 fix from Mark van Doesburg.

Eeschema: fix bug in load_one_schematic_file.cpp: error about files version, that create errors for hierarchical labels.
Pcbnew: cleaning code in block.cpp, and modifye previous way to calculate block size in block command, because old way creates unexpected behavior in block rotate and block flip.
Pcbnew: Fix a bug in plot silkscreen layers.
Cvpcb: Fix compilation issue under MACOX

Fix bug in PolyLine.cpp, Fix bug in DRC calculations (see changelog). Cvpcb: move dialog files in dialogs/

Fixed some issues about trapezoidal pads. Better pad editor dialog. fixed other (very) minor bugs. Code cleaning

inches and mm, the industry is crazy enough to force us with mixed
design. For example I routinely use imperial units for track size and
clearance, but drilling is strictly a metric issue...

So I added a little parser to recognize a suffix specification in the
unit text boxes... so you can put in things like:
1in (1 inch)
1" (idem)
25th (25 thou)
25mi (25 mils, the same)
6mm (6 mm, obviously)

The rules are: spaces between the number and the unit are accepted, only
the first two letters are significant.

As a bonus, it also recognize the period (.) as a decimal point
substituting it with the correct locale character (there was a wishlist
for it, IIRC). Most useful for number pad fans :D 

* Fix a minor problem with wxFileDialog to open a file that no longer
  exists in PCBNew.
* Make GerbView open file behavior the same as PCBNew.
* Remove redundant PCB file wild card definition.
* Add open file refactor task to the todo list.
* Fix some minor code formatting issues.

* Make USE_WX_ZOOM clipping routine actually clip rather than just test
  if line needs drawn.
* Clean up as many USE_WX_ZOOM #ifdefs as possible.
* Minor coordinate rounding improvements.
* Minor scrolling and panning improvements.
* Remove unused KicadGraphicContext object code.

* Implement code to allow wxDC to handle coordinate conversions between
  device and drawing units.
* Add build settings to enable wxGCDC for wxGraphicsContext testing.
* Remove wxAUI conditional build cruft as it is now required to build
  Kicad.
* Fix scroll increment size regression to prevent jumping around the
  zoom center position.
* Add find GDI+ cmake module for building on WXMSW when wxGraphicsContext
  is enabled.

hide/show rastnest in pcbnew is currently not working, will be fixed soon

* Remove redundant background redrawing RedrawActiveWindow.
* Remove redundant managed cursor callback in RedrawActiveWindow.
* Use refresh to redraw instead of directly calling RedrawActiveWindow.
* Remove unused SetDrawBgColor for drawframe.cpp.
* Fix compiler warning in cvpcb/cvframe.cpp.
* Fix menu spelling and syntax errors in pcbnew.
* Rename Trace_Curseur to DrawCursor in common/drawpanel.cpp.

Added patch for macOSX
turn on fast algo for draw grid (should work now)

* Fix debug asserts when passing NULL pointers to wxAuiPaneInfo.
* Fix Kicad main window sash sizer bug when using wxAui.
* Remove specctra_test from Visual Studio builds to prevent build errors.
* Add WIN32 to layer widget test so it will build properly on Visual Studio.
* Fixed compiler conversion warnings in PCBNew.
* Fixed worksheet print scaling in PCBNew.
* Minor code renaming.

others minor bugs fix.