- add a generic code generation tweaks facility. Rework the Thrift exception tweak to use it.
- add a code tweak for the Closeable interface, remove the hardcoded method from the templates.
- add a code tweak for extending RuntimException instead of Exception.

- update maven plugin to allow all tweaks.
use latest released base pom
Merge branch 'master' of github.com:facebook/swift

Conflicts:
	pom.xml
Merge pull request #47 from hgschmie/master

add a generic generator tweaks code facility