Implement Transaction Model and repository

[0xsarvesh]

Proposal

Definition:
1. Id: Auto increment
2. Transaction hash
3. Entity Type(Message, Requests) // Please validate if this is needed, this info can be derived from action Type.
4. Action Type(
AcceptStakeRequest, ConfirmStake, ProveGateway, ProveCoGateway, ProgressStake, ProgressMint)
5. Identifier(i.e. primary key like MessageHash, stakeRequestHash)
6. Status (Submitted, SubmissionFailed, Confirmed, Lost, Retried, TimeOut)
7. Retry count

Status can be defined by implementor