add failing drop_master_while_maintenance
make sure lease expired event keep forever flowing through the state machine
prevent slave from ignoring duplicate message from master
a bit more info logging
Logging more Paxos at info level
Merge branch 'incubaid-1.6' into masterless

Conflicts:
	src/node/mem_store.ml
	src/paxos/slave.ml
	src/system/drop_master.ml
comment from PR
Merge pull request #460 from Incubaid/masterless

Masterless
Enabling non-LWT logging

Code mostly imported from 1.7 branch, specifically rev.
037abb4024f64af8cd86a3d57668283cefd87598, to reach a state similar as to
the one seen in rev. 186bd73659f277947cf2a95fe71bec27e15d27dc.
Logging embedded in statistics
Merge mark-christiaens/logging into 1.6 (using imerge)
Fix compilation
fix for multiple masters issue by respecting the paxos logic