Drop support for OCL expressions

[pcdavid]

Note: this is just an idea for then moment, there is no hard decision yet. If you actually depend on OCL expressions in Sirius Desktop odesign files, please mention it.

We support using ocl: expressions in VSMs through org.eclipse.sirius.common.ocl, but I'm not actually aware of anybody using this concretely. Although this support does not create an explicit maintenance burden, it's one of the dependencies we could probably remove without much impact to simplify things on our side.

Additionally, the future of OCL itself at Eclipse is uncertain at the moment, so if at some future point OCL is dropped from the SimRel or otherwise becomes a liability, removing the dependency would prevent any such impact.

Note that we actually have quite a few of our test models which use ocl: expressions. If they sepcifically test for OCL compatibility they should be removed as part of this, otherwise they should be transformed into aql: expressions (ideally a simple search & replace, but some seem complex enough to have different behaviors in the two languages).

[pcdavid]

Note that #439 is one more reason for removing this bundle. The workaround required to support both old and new versions of OCL is ugly.