Refresh of the index interface.
Make object lookups idempotent if the oid is already the class of the
correct type.
Revert "Make object lookups idempotent if the oid is already the class of the"

This reverts commit e20455b27bf19492b8e225d71cf70913a036866f.
Allow oid or tree objects when making a commit.
Rename get-tree to commit-tree.  Since it seems that only commits will have trees associated with them.
Minor doc cleanup.
Renamed tree-mixin to pathname-mixin and added it to the api.lisp.
Fixed bug with tree listing, when tree type doesn't have the correct mixin.
Added index capabilities function.
Pure lisp version of the index stage calculation.
Add function to get the status of a file by path.
Fixed typo in documentation.
Reformatted some of the remote API.
Fixed namespace issue with odb documentation.