Extract the create id funtionality into a public method
Replace #getorCreate with separate #get and #create calls
Implement uid allocation in the MemoryStore
Remove the UniqueId mocking in the TSDB tests
Cleanup some imports and document #createId in UniqueId
Merge pull request #8 from hi3g/remove_getorcreate

Replace #getOrCreate with separate calls to #get and #create