Add first steps for ex(C) for CommWait

Add first steps for ex(C) for CommWait

Computing the extension sets of a `CommWait`
action turns out to be a bit more involved than
I anticipated. In particular, we must determine
whether or not the transition is enabled at
some point in the past. This requires us to
find the event which created the communication
on which the `CommWait` waits and perform a
couple checks on that event. The current implementation
is not complete and is missing several important
steps, but it's a step in the right direction.

Additionally, some Sonar errors were fixed.