JBoss Runtime detection should not assume all plugins are available especially with drools and jbpm plugins being separated out for SOA pack.

Copied from JBIDE-8456:
2. org.jboss.tools.runtime

It contains a plugin that implements the JBoss AS, Drools, Seam and jBPM detectors and depends on AS, Drools, jBPM, Seam and JBoss Runtime Detection Core.

The problem was because JBDS installer detection wasn't separating AS runtime within EAP, EPP, SOA-P ... from Seam, Drools, jBPM runtimes. I have inherited that code.
Because of that, all these detectors are included in the org.jboss.tools.runtime plugin.

If we want to separate those dependencies, we need to do the following:

separate the Drools, Seam, jBPM detectors from the AS/EAP/EPP/SOA-P detector
move runtime detectors to separated features (the AS, Drools, jBPM, Seam, ESB feature or some new features)
change the JBDS installer detection code according to these changes

As to optional dependencies, P2 treats them as hard dependencies. If IU exists, P2 will install it no matter if it is optional or not. Currently only the drools dependency is optional.