Fixed bugs 2981754 and 2981759 (PCBnew crash when trying to add a new net name to a pad) Linux specific, and perhaps due to a bug in wxGTK 2.8 (does not happen in 2.9)

* Some bugs fixed
* Starting enhancements in Libedit: menubar and commands to "plot" current component in PNG or SVF file (SVG file not fully working, must be refined)

default is Edit pin per pin for components with parts locked and coupling pin for others.

This patch applies on the very last svn  (r2402) and removes all
disfunctionnal python code (including deletion of unused strings)

All: fixing a recent problem when using scroll bars: the full screen was redrawn, that can be very slow in Pcbnew.

Added sample gerber files for test (gerbview has problem with 2 files)

Pcbnew :added option to show/hide footprints values and/or references

Removed old color and visiblity dialog
work in progress.
See also TODO, P0)

    * in variable names, change non existent word Hight to High
    * Remove redundant tool in left toolbar (option toolbar)
      (this option is now in layers manager)
    * Show layers in horizontal combo box in same order as in layer manager.
++all:
    minor code cleaning.

fixed minor problems and fixed Layer Alignment Target bug.

patch for relative paths.

Code cleaning.
Patch for 3D problem with macOSX

files cleaning

Fixed others minor problems