Conductor logging enhanced (MRN-713)

"Rule" tags have got additional parameter ("desc") which is supposed to contain
a human-readable description of the rule - i.e. which entities the rule should
match in the data (without it the rule can be identified only by its "match"
statement, which is absolutely unreadable).
Existing workflows have got some approximate descriptions in their Rules.

These desc's  are logged (at DEBUG level) when the rule is matched against some
data - the matched data is outputted as well.
Also, additional logging messages added in various locations to do some
excessive logging of conductor operations (setting context values, reporting,
state transitions, waiting for RMQ messages).

As the result, the conductor's log (if  HeatClient messages are grepped out)
should contain a detailed explanation of conductor's states and the execution
routines.

Change-Id: I8d4794f522d4218cf58206682cfc9c0ca0f4b102