Fix for the following issues raised by Quentin. Mostly documentation fixes.

- About -shouldMakeEmptyCommit… The documentation sounds vague by using 'would':  Would be used to cause a "checkpoint" revision to be written. Doe that mean the usage is uncertain?
	- Changed wording

- Not sure it's useful to keep -canUndo, -canRedo, -undo and -redo in COBranch.h since the public API is inherited from COTrack
	- Removed

- Provide examples for applying diff from -mergeInfoForMergingBranch: and -mergeInfoForMergingRevision: (see API doc)
	- Added "not finalized" comment. Also added to COMergeInfo

- For the following, I prefer to use [self initWithStore: nil] pattern since it means we transparently follow the designated initializer constraints. For example, if we decided to support a nil store later, -init will behave correctly without any changes.

- (id)init
{
	[self doesNotRecognizeSelector: _cmd];
	return nil;
}
	- Fixed

- What about the FIXME comment for -didCommitWithCommand:persistentRoots:
	- Updated and changed to NOTE

- Status of the FIXME in -objectReferenceWithUUID:?
	- Fixed

- Attempting to set a value for a readonly property should raise an exception <-- This was removed from the TODO list, but I cannot find the code to detect this issue in COObject
	- Re-added

- Remove "Support transient persistent roots" from TODO



git-svn-id: svn://svn.gna.org/svn/etoile/trunk/Etoile/Frameworks/CoreObject@9864 7b3f36aa-e6db-49c1-8b4c-66eac1997e64