Update statdb args/return values to minimize structs
Simplify statdb.Update() to update all stats instead of an arbitrary subset determined by flags
Remove CreateIfNotExists logic from statdb.Update()
Simplify audit code structure
* intial changes to migrate statdb to masterdb framework
* statdb refactor compiles
* added TestCreateDoesNotExist testcase
* Initial port of statdb to masterdb framework working
* refactored statdb proto def to pkg/statdb
* removed statdb/proto folder
* moved pb.Node to storj.NodeID
* CreateEntryIfNotExistsRequest moved pd.Node to storj.NodeID
* moved the fields from pb.Node to statdb.UpdateRequest
ported TestUpdateExists, TestUpdateUptimeExists, TestUpdateAuditSuccessExists TestUpdateBatchExists
