Fix some coverity and cppcheck warnings (most are very minor issues: not initialized members and initialized but not used variables)

The hotkey import/export files have now the extension ".hotkeys"

Footprint editor: set the default footprint text size to 1 mm. Minor cleaning code. Very minor other fixes.

Fix some minor coverity warnings. Fix a bug in pcad2kicad plugin. Scripting: map BASE_SET. Rename some python bom scripts with better names. Fix erroneous comments and add comments

* Add wxTAB_TRAVERSAL to TREE_PROJECT_FRAME ctor.
* Please note that there is still a focus issue when closing a child window (at least on
  windows) that prevents this from being an ideal solution.
* Minor code cleaning.

Eeschema: Fix a (minor but annoying) bug detected by coverity which prevent Eeschema to draw components in "fast mode" (i;e. without pin texts) when they are moved, due to a draw parameter which was incorrectly used.
Move items rework: enhancements: for some items (sheets, components, bus entries) the mouse cursor is no more wrapped to the anchor. For large symbols, this is better: they are more easy to place.
There is also a change when starting a move item command: the full screen is redraw, and therefore there is no artifact due to the XOR draw mode.
Some other minor coverity fixes (uninitialized members).

* Fix default KISYSMOD/KISYS3DMOD (#ifdef typo) for OSX builds.
* Remove setting KIGITHUB from kicad/pcbnew Info.plist in favor of hardcoded default
  setting for OSX builds.
* Remove now unneeded Set3DShapesDefaultPath() and other small things.

Fix some coverity warnings (not initialized members). Add comments. Better (more informative) title in dialog to download .pretty libs.

Fix someminor  coverity warning, and one bug found by coverity in drill report files : buried holes were not properly counted and listed.

lib_dxf: Update to version 0.5.13 (previous: 0.5.11) due to a bug (memory leak) fixed in 0.5.13, which has also more comments, and try to fix most of coverity warnings (not initialized class members).
These members are now initialized, which also fix some other more serious coverity issues.

pcbnew, place file: Fix a minor bug in side identification: a comment in file header was generated with always "top side" id even when the bottom side file was created. Fix also a minor coverity warning (no bug)