Speedup for Grease Pencil animators.

Saving and loading gpencil was using different order for the individual list items.
On a 120 Mb gpencil project (yes, animators!) loading time went down from 1 minute 
to a second or two.

Note that this to have effect, you need to save once.

Developer note: check this commit, it uses a new writelist function. You can 
speedup stuff tremendously with keeping saved and read data in sync.



git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@55092 954f8c5b-7b00-dc11-b283-0030488c597c