Connectors shouldn't try to manage the same thread pool

* app connectors use the server thread pool (null means inherit thread
  pool from server)
* admin connectors have their own shared thread pool that is now managed
  by the server instead of the individual connectors

Having multiple connectors manage the same thread pool was problematic.
To reproduce, run the example application and send a SIGTERM to the
process after it starts. It will timeout and give up stopping the admin
thread pool after 30 seconds instead of stopping cleanly right away.
Merge pull request #415 from vadims/connector_threadpool

Connectors shouldn't try to manage the same thread pool
Updated dependency on liquibase-slf4j to 1.2.0
Upgrade of liquibase-slf4j from 1.2.0 to 1.2.1
Merge pull request #424 from wirde/master

Updated dependency on liquibase-slf4j to 1.2.0
Fix comparison of elapsed time and threshold in SlowRequestFilter

Fixes #423
Merge pull request #430 from joschi/issue-423-SlowRequestFilter

Fix comparison of elapsed time and threshold in SlowRequestFilter
Fixing formatting
Fix issue when we specify duration twice.
Merge pull request #435 from alex-bezrodniy/CsvReporterFactory_bugfix

Fix issue when we specify duration twice in CsvReporterFactory.
Handle deserialization when enums are lower-/mixed-case
Added the ability for the configuration factory to be customized. This
will allow you to use custom configuration formats as well as intercept
the configuration generate to change it programmatically at runtime.
Add support for customizing the view renderers used
Upgraded to Jackson 2.3.0.
Upgraded to Jersey 1.18.

The dependency exclusion for com.codahale.metrics:metrics-jersey in
dropwizard-jersey should be removed as soon as the same Jersey version
is being used in Metrics. Otherwise the Maven Enforcer plugin is very
unhappy about it.
Upgraded to Jetty 9.0.7.
Upgraded to JSR305 Annotations for Findbugs 2.0.2.
Upgraded to Java EL implementation 2.2.6
Upgraded to argparse4j 0.4.2.
Upgraded to Apache HttpClient 4.3.1.