Rename saveAndGetData to getBlockData, hopefully this is more descriptive and because saving is an implementation detail

Saving feels like implementation detail, getData() is the main public method for getting the data and in most cases users will want that data to be saved in the store as well.
Fixed wording in tests
Renamed saveAndReturnData to getData, hopefully this is more descriptive
Remove setAndRetrieveData because it's not used anymore
Add some comment docs for BlockStorage methods