Move maintenance provider and districts to Transit engine
Add TransitAsset class to provide methods to store how transit assets were purchased.

Move purchase cost, purchase date, in service date, purchased new to Asset
Move ServiceType from core to transit
Add grants tables and move funding source tables from Core
Remove tables no longer needed
Clean up asset models
Move funding sources controller and views from Core
Merge branch 'master' of https://github.com/camsys/transam_transit
Clean up seeds etc so all the tests run