Merge conflict resolution.
Outstanding changes.
Remove context from dispatches.
Use protocol instead of structs to represent cluster change commands.

Commands of a state machines are represented with cocaine io protocol. Actually cluster configuration is a state machine, so its commands are also represented with protocol now.
Service counter replies with usefull error codes.

Service counter replies with raft::command_result, so client can determine, what type of error has occurred and where is the leader now.
Merge pull request #80 from andrusha97/raft

Raft
Fixed warning about unused private field.

Because of we treat warnings as errors it results in compile error.
Codereview, part one.
Service resolver no longer requires `context_t` object.
Merge pull request #81 from 3Hren/master

Fixed warning about unused private field.