Created simple state tracking class SpendStateMgr.
Also: remove stale comments and test code from sendpayment.
Also: don't continue aborted Taker in stallMonitor.
Also add detailed function definitions for Taker callbacks in
taker.py comments. Modifications to joinmarket-qt, tumbler
working but these modifications not yet complete.
Introduces an additional jm_state to avoid resending JMTX in case
the response to checkUtxosAccepted takes too long.
Fix bug in -Qt where blockr wallet sync is called with fast option.
Make unconfirmed message more informative (more TODO here).
Fix bug in blockr_data (from upstream).
Adam Gibson