Automatic execution of SCL tests in Maven

This includes both compiler tests (in
tests/org.simantics.scl.compiler.tests) and a test that checks that all
SCL modules in org.simantics.sdk feature compile (in
tests/org.simantics.scl.osgi.tests).

This commit contains also some modifications to make all SCL
modules compile:
* Disabled Data/Json, because it does not compile (missing jackson)
* Committed away Simantics/Image/linkImage

Change-Id: I22a460d756f65139971f1e7d2cc8624a7a6b8ffb