Redesign of how to fetch Tags

Tags (so, Weather, Time of Day, and other keywords) associated with a Haiku are now represented in their own model class.
Introduced concept of a DataAccessDelegate, which a model class can use to construct itself.
This is done with a protocol, and then I have SLLite implementations.
Not sure how well this would work with CoreData if I ever went to that.
But, it would work well if I introduced a WebService to provide the data instead.

Signed-off-by: Ippoippo <ippoippo-software@ippoippo-eco.com>