Factored checkstyle config into it's own mvn project

Factored checkstyle config into it's own mvn project

This allows correct handling of multimodule checkstyle as
documented here:

http://maven.apache.org/plugins/maven-checkstyle-plugin/examples/multi-module-config.html

This involved:
- Adding a commons/checkstyle module to hold the space_and_tabs_checks.xml
- Altering commons/opendaylight to use commons/checkstyle
- Altering commons/concepts to use commons/checkstyle
- Altering commons/integrationtest to use commons/checkstyle
- Altering opendaylight/distribution to make sure to build commons/opendaylight
    and commons/checkstyle
- Altering opendaylight/distribution to exclude commons/checkstyle from the
    distribution zip file.

Change-Id: I36c23fc92ab8ec711861c7e9251a63b1aa60fd40
Signed-off-by: Ed Warnicke <eaw@cisco.com>