2.5 - Start of porting of Animation Editors

2.5 - Start of porting of Animation Editors

* Added new 'Animation' submodule under Editors. This will be used to house all code + features that are used by many different Animation Editors (Action/Dopesheet and IPO) as well as other parts of Blender.

* Added back some of the core code need by the Action/Dopesheet editor, which will also be used by IPO Editor.
* Brought back file for keyframing management code (i.e. keyframing.c), but there's still quite a lot of missing stuff that I'll need to restore, so in the meantime, it's #if 0'd out.

* Moved markers code to this new module (I'm not sure whether SVN will recognise this change, as TortoiseSVN doesn't seem to have any obvious copy/move commands)