Include filter/output class name in skip/drop debug log messages

Bit distressing to see log messages like 'Skipping event' without seeing
*what* is skipping it!
inputs: rabbitmq: fix optional exchange binding

Make hot_bunnies implementation behave the same as the bunny
implementation: optionally bind the input queue to the output exchange
if the "exchange" option is defined.  If it is not defined, some other
out-of-band process will need to setup the bindings.  Remove the
backward-compatibility reference, because this is actually a useful
feature to continue supporting.

LOGSTASH-1300
Merge pull request #627 from doismellburning/include_names_in_drop_skip_logs

Include filter/output class name in skip/drop debug log messages
Update tutorials for logstash 1.2.x
an edge case
Use 'message' as the default field
- add tests to cover grok singles with duplicate field names
- fix an edge case where you have something that captures a few patterns
  to a named field, like (%{INT:foo}|%{WORD:foo}) and it only stores one
  and as a single value.
Merge pull request #624 from jdve/master

inputs: rabbitmq: fix optional exchange binding
- restore multiline filter from 1.1.13 (LOGSTASH-1297, LOGSTASH-1285)

It may go away in the future, but it was accidentally removed in the
1.2.0 release and its accidental removal caused backwards
incompatibility, which is bad and I should feel bad. </zoidberg>
.
prep for release
Merge git://github.com/logstash/logstash