Gpf

- Completely redesigned and improved the Where class (queries module)
- Added missing docstrings to all classes in the cursors module
- Fixed fieldutils module

- Added support for in-memory workspaces.
- Improved lookups module, allowing users to more easily create their own Lookup subclasses.
- Added ValueSet to lookups module.
- Removed containers module.
- Minor fixes and improvements.

This release features several new functions in the "fieldutils" module:
- clone_field()
- list_fields()
- add_field()
Furthermore, some global constants that were specific to a module but might be useful for other modules too, have been moved to the "const" module.

This release contains updates for the metadata module (Describe wrapper) and several bug fixes.
The lookup module features a new class called NodeSet, which builds a unique set of coordinate hashes for a given feature class. Furthermore, the coord_key() function in the lookup module has been renamed to get_nodekey() and now accepts Point and PointGeometry instances, a JSON dictionary or an iterable of floats.

First stable (beta) release