Refactored the JarToSrampArchive (artifact expansion) code to make it
pluggable (using java serviceloader).  Now additional implementations of
JarToSrampArchive can be contributed (e.g. the switchyard integration
module can contribute its own impl).

Also improved the sramp ui config a bit (constants).
Merge pull request #76 from EricWittmann/sramp-expandedFromDocument

Made JarToSrampArchive pluggable (artifact expansion)