localization updates, new features, bug fixes

Script now handles localization much better
New features to support maintaining main menu system includes new action
(settings), new property (labelID), new shortcut group (common) and more
Numerous bug fixes
Conditional visibility for main menu items, updated readme

Common items for [groupname] mainmenu will now display based on
conditional visibility, so live tv won't show if no pvr manager is
enabled, for example.
Fix errors in readme
Support for overriding actions, minor bug fixes

Skins and users can now provide override.xml to override actions based
on XBMC boolean conditions. See readme for full details.
Option to reset all shortcuts, type=settings now refreshes after update, overrides stops processing after an override is run
Fix error in readme
Checks if user has shortcut to settings

Script now checks if the user has a link to shortcuts in their
customised menus, and sets a window property so skinners can provide
alternative access.
Allow skinners to override default images, list of labelIDs
Bug fixes

No longer use elementree.iterfind (Mac fix)
When run as plugin, always return directory item (fix for plugin ended
prematurely error)
Cleanup logging
Fix for overrides on Mac, begun moving to xbmcvfs
[Fix] Media now keeps playing when selecting a shortcut
xbmcvfs, updated some localised strings, bug fix

[Update] Now uses xbmcvfs to load and save all shortcuts, delete all
files
[Fix] Corrected localised strings for 'Programs' and 'Timers' (Thanks
BigNoid)
[Fix] Media keeps playing when resettings all shortcuts
Correct labelID list
Favourites listed by JSON, bug fix

Favourites are now retrieved by using JSON, rather than directly reading
and parsing the file
Fix rare condition when editing a specific shortcut, where the changes
would be saved to the wrong item if the user switched focus in the list.
Quick-fix for no favourites/no add-ons
Cleanup defauly.py code, proper fix for no favourites/ no add-ons
Added two propertied to listitem's - action and group
Speed improvements

Various tweaks for improved speed, most notably processed shortcuts and
override files are kept in memory
Use visibility conditions to speed up sub-menus

When using script to provide whole menu system, use new type=submenu to
list submenu. See readme.
Using video nodes to list video library shortcuts, fix main menu item visibility, version information in readme

Testing using video node files to list shortcuts to all parts of the
video library - this WILL break some overrides (both action and image),
and behaviour WILL change in future. See readme for details.