Multiple undo/redo is now possible

The 'Undo' and 'Redo' aui tools are now dropdown. Their menus show the relevant command history descriptively e.g. Undo deletion: "Foo"
Any 'states' with a user-set label can now be seen and 'goto'ed from their own menu
Changes to help the UnRedo system work in plugins (i.e. wxCrafter)

Some things are now delegated to the CommandProcessorBase class.
Also includes some bug-fixes.
More changes to help UnRedo work with plugins; this time 'frame-mode' wxCrafter

Also, removed the md5sum code, as it's not going to be used in the forseeable future.
Merge branch 'multipleunredo'

1) The Undo and Redo tools are now dropdown, so it's now possible to undo/redo multiple changes at a time. Each change is shown as 'Insert "foo"' or 'Delete 13 chars'.
2) There is a new item in the Edit menu: 'Set label for current state'. This allows the user to set a more-readable label for the current state e.g. 'Before adding debug code'. This makes it easier to select the correct 'undo to here' point.
3) To make undoing/redoing to a particular point even easier, when there are user-labelled states an extra submenu appears below the 'Set label for current state' item, containing all user-labelled states.

Conflicts:
	LiteEditor/frame.cpp