Pcbnew: add drc test for texts on copper layer (only in full drc test, not in on line drc), from a patch sent by Simon Schumann
Add EDA_TEXT::TransformTextShapeToSegmentList function to export a list of segments used to draw/plot the text.

* Improve footprint text properties layout.
* Use wxStdDialogButtonSizer instead of manually laid out buttons to improve
  platform UI consistency.

Pcbnew, Cvpcb: fix Bug #1355883 . Due to a missing call to a delete operator in CMP_READER class (also creates memory leak).

3d viewer: fix a (minor) bug when run from cvpcb or modedit: the footprint is now centered on Z axis
Better setup for lights, which gives a better rendering

2) LIB_RECTANGLE and related classes sscanf data read from a file using "%s"
without field limits, which can cause problems with malformed/really long
inputs.

3) If some of the optional fields in a lib line are missing, "tmp" can remain
uninitialized.

3D viewer: Parallelized 3D model vertex normal calculations to use all available CPU cores for significant speedup.

Pcbnew: Commit patch (with very minor changes) about SVG file export with the layers ordered from bottom to top. ( bug 1286646 ), from Thiadmer Riemersma.

3dviewer: back to double (from float) in class S3D_MASTER for 3 members (m_MatScale, m_MatRotation, m_MatPosition) which are used in dialogs and r/w file functions, which expect double.
Using float create minor but unwanted issues in  r/w file functions.
S3D_MATERIAL: enable all color options: if a 3d shape has bad color parameters, the shape must be modified, not the 3d rendering.
The rendering now matches what we see in other vrml viewer like FreeCAD.
Some minor coding style fixes.

Items are either dragged by their origin or moved by a vector (depending on the number of selected items) (GAL).

common.cpp: remove useless  warning on wxWidgets < 3.0 about --with-gtkprint build option: on  wxWidgets < 3.0 on Linux the print function does not work even with this build option.

3D viewer: move helper functions from 3d_draw.cpp to 3d_draw_helper_functions.cpp. Add comments in .h sources. Better management of background color. coding style fixes.

Add comments. Fix bug  #1351507 (pad color does not reflect, whether the pad is on front or back layer) and bug #1351388  (Adding a keepout area appears on the opposite layer than selected)

dialog_track_via_size: set minimal size  and make dialog resizable.
Update demo file.