Feature/soledad adbapi3

DO NOT MERGE YET
just for testing / pullreq purposes

no we're not.
As I commented somewhere above, there's something missing here that has to do with returning a deferred from certain initializations that inform the caller when the initialization is complete (this is going to be needed to get upper layers like mail working, but we'll need to have a specific testcase in soledad client too).
Another options I am considering:

* Registering a whenReady callback (in a similar way to reactor.whenRunning, or whatever it's called).
* Implement a retry mechanism with callLater and retry_count/fail.