Bug 651 - Added back IDE profile and changed target for yang sources

- The IDE maven profile was added back based on feedback from Giovanni Meo

- To avoid devs from having to run the IDE profile so eclipse can see the yang
generated source files, the yang source files are now generated under src/main/yang-gen-sals
or src/main/yang-gen-config instead of target/target-ide.

- The maven-clean-plugin was moved to the commons base pom and removed from
all child poms where it was specified. Thus, it will be automatically run for all
projects. The plugin's execution will clean all xtend and yang generated source dirs.

- The build-helper-maven-plugin was also moved to the commons base pom and removed from
all child poms. It will automatically run for all projects and no longer needs to be
specified in child poms. The plugin's execution will created eclipse source folders
for all xtend and yang generated source.

Tom P and Devin A really did all this work, Greg just gets credit unfairly.

Conflicts:
        opendaylight/config/config-module-archetype/src/main/resources/archetype-resources/pom.xml

Change-Id: I8d9e403629cab2e48d03d5c7a417a02f1d878ca7
Signed-off-by: tpantelis <tpanteli@brocade.com>
Signed-off-by: jameshall03885 <ghall@brocade.com>
Signed-off-by: dbavery <devin.avery@brocade.com>
Signed-off-by: jameshall03885 <ghall@brocade.com>