fixed database field names to m. instead of md.
refactored response to a standard response; setting of principal created date from db NOW() to time.NOw() in PUT
implemented responseAPI type into projectcurrency and user
Merge branch 'master' of github.com:fritzpay/paymentd into payment_method
added provider api and doc; fix doc for currency api
Merge pull request #28 from chruffer/provider_api

Provider api