Minor enhancements.

They are now member of EDA_DRAW_FRAME.
This change could fix Bug #1330781 (Background color change in Eeschema affects background color in Pcbnew)
Show page limits has meaning only for the schematic editor,  the board editor and the page layout editor.
Draw background color selection exists only in eeschema and  page layout editor.
In pcbnew, only a black background is allowed.
A side effect is now the user should set the background color in schematic editor, and the library editor (2 different options).
The default is still the white color.

Gerber X2 patch (Support for the "file function" attribute) from Thiadmer Riemersma, committed in rev 4948: minor fix for better compatibility with older versions of Pcbnew

Pcbnew, python console: make it not dockable (workaround to avoid the fact accelerator keys which are used in the main menu are not sent to the console, in docked mode).
Minor cosmetic enhancement.

Pcbnew, python console: make it not dockable (workaround to avoid the fact hot keys which are used in the main menu are not sent to the console, in docked mode)
Minor cosmetic enhancement.

Minor cosmetic enhancement, and try to fix an issue with accelerator keys and the Python scripting console

In KIFACE_I::end_common save the 'common' configuration variables loaded in KIFACE_I::begin_common (the background color and the page border flag)

- Refactored the common part of cursor key movement and crosshair update
  in the various GeneralControl
- Add x10 movement with the keyboard (CTRL modifier)
- Avoid fixup of the cursor position by dummy mouse movements generated
  by cursor warping (original analysis and idea Chris Gibson)
- Do key handling in a way to permit sub-pixel cursor movement 

   to a new BOARD in the footprint editor.  This is PAGE_INFO::A4 and company.
   
*) Remove static storage of the BOARD in the module editor.

Change class PROJECT to use a generalized wxString in place of the
RETAINED_PATH items, so that new session and project specific strings
of any purpose can be saved there, for the life of a session.

Page layout editor: fix bad initialization on startup, which can crash pl_editor when trying to edit an item.
Minor other fixes.

Fix segfault when deleting last user path from eeschema libpaths and then pressing cancel.