Adapt FishingSession and Fish fields to match existing data
expectations.
Remove fish weights and make length a value type.
Move data validation into Fish.
This works now that fish aren't interdependent on any session data.
Relocate existing data providers and add storage service and management.
Actually add service and manager.
Merge pull request #5 from MrDOS/master

Bring data definitions up to speed and add persistence interfaces.