Removed Container interface. Renamed Location to IDComponent. Created a new type Location, which embeds IDComponent. Cleaned up h5p.go
Made Datatype a Location.
Merged h5l.go with h5i.go since there wasn't any code in h5l.go
Add Type() method for IDComponent.
Renamed IDComponent to Identifier, in deference to the C API. Made Table a Location.
Merge pull request #11 from echlebek/master

Refactored the object hierarchy, and added some methods that apply to all API types.