Fixes to communicator package as suggested by @illarionov

* Changing context scope.
* Moving closing cursor and submitter command into finally{}
* Deciding that all IOException` can be temporary (reduces data discarding).
* Cleanup if gzip fails: if gzipping fails, the AbstractCommunicator has to clean up first.
SyncAdapter will not delete records on error.

* Assume all errors from cleanSend() are potentially temporary.
* Do not delete anything while sending.
* cleanSend() will Log.e errors.
Merge pull request #474 from tamcap/network

Fixes to communicator package (@tamcap, @illarionov)