DATAMONGO-833 - Add support for reading EnumSets and EnumMaps.

Switched to use Spring Data Commons' CollectionFactory that is capable of creating EnumSets and EnumMaps. Added unit test inspired by pull request #113 for EnumSets and an additional one for EnumMaps.

Slightly refactored the algorithm for reading maps to prevent repeated type lookups.

Related pull request: #113.