Initial RevertOp implementation.
Added initial unit tests for revert.
Fleshed out revert implementation

Added more unit tests
Basic cli command
Functional tests
Man pages
Fixed issues with empty type trees

Fixed an issue which caused empty trees to not import.
Fixed an issue which caused commit to not move the feature type of an empty tree to the object database.
Merge remote-tracking branch 'jdgarrett/revert'
Updated unit tests and implemented rev-parse type verification
Merge remote-tracking branch 'jdgarrett/EmptyTrees' into mergeme