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.

Add patch for 3D viewer enhancements (better render + better vrml reader + x3d reader bug fix) from Mario Luzeiro, with few coding style issues fixed.

Remove a minor warning message in Debug mode for 2 dialogs.
Pcbnew: update Gerber X2 file format (File Attribute) to very last X2 specification
Eeschema: Fix a minor bug in block selection (sometimes the last selected component was select instead of items in selected area)
and better drag behavior when draging an item by the drag hotkey.

and forces absolute path.

2) PNS router incorrectly detects collisions with blind/buried vias that don't actually intersect the active layer
3) PNS router silently converts blind/buried vias to through-board vias when shoved

Eeschema fixes: fix  Bug #1348983 save cmp file crashes cvpcb when eeschema is opened (backannotation crashes). Happens only when some footprint names are not set (blank names).
Also fix incorrect backannotation when footprint names contain spaces (put spaces in names is always a bad idea)
* Fix minor Bug #1349058 Choose component dialog: Search field loses focus after entering a character and internationalize the dialog.
* Fix a subtle bug which prevent eeschema to read the project config file when launched from kicad manager, and when kicad.pro is not found.

* Fix Bug #1348607 and a possible crash in libedit dialog component properties after moving up the first user field (which in not possible now).
* better info message in pcbnew when trying to delete a footprint in legacy library

ModEdit: fix some issues due to the fact legacy footprint libraries cannot handle 32 copper layers, and are therefore no more editable:
* in file/library save as..., remove option to save a lib under the legacy format (which is not possible and creates an error message)
* if the current loaded lib is a legacy lib, when the user try to save or delete a footprint, displays a message which explains what the user should do.
* add a suitable dialog to select/create a .pretty folder library (a file dialog or a dir dialog coming from wxWidgets is not friendly usable.)

3d viewer: Add high quality mode option is realistic mode (Shows holes in copper zones, but with longer calculation time)
Gal: fix a very minor issue: the keys to switch between copper layers are now - and + (according to the doc and the normall mode), instead of - and =