Merge pull request #182 from adityab/edit-close

Have dedicated Editor.closeDocument and Editor.closeSession
New operations: OpAddMember, OpRemoveMember.

Member data is now handled in a memberDataManager
instance inside OdtDocument.

Any operations must be executed only if a member
is present within this model.

All polling code for member data has been removed;
colors, names, and images now instantly update
whenever a member data operation is executed.
Remove terrible hack for setting the dc:creator
field's text in an annotation; now that we
have first-class access to member data,
we can set this value directly within
OpAddAnnotation.