[EPIC] Data persistence

[jackzampolin]

Currently goridan is implemented with in-memory data stores. In order to have a production implemetation we need to enable persistence. SQLite support for Gordian data persistence is the first target. The tables should be all independent of one another making the translation to SQL straightforward. Initial implementation should be hand written SQL. The following interfaces need implementation for this epic.

• ActionStore - tm/tmstore/actionstore.go
• BlockStrore - tm/tmstore/blockstore.go
• FinalizationStore - tm/tmstore/finalizationstore.go
• MirrorStore - tm/tmstore/mirrorstore.go
• RoundStore - tm/tmstore/roundstore.go
• ValidatorStore - tm/tmstore/validatorstore.go