Have DateDimension have a dimensionId that is based on the natural key

Currently the record sequencer (delegator.getNextSeqId) is used to determine the dimensionId for the DateDimension. This is unnecessary as the date (when correctly formatted) can be used. 

When formatted as 'yyyyMMdd' a dimensionId could be 20190423, which is a correctly 'sequenced' primary key.
It also makes it easier to set the foreign-key in fact tables by generating it based on the date, than by retrieving the dimensionId based on a retrieval through the getDimensionIdFromNaturalKey service.