WIP: Add tests for Context creation with services

=== SOME OF THESE TESTS FAIL ===

We check that contexts get created (or not) in various situations,
with service dependencies of various natures.
Inject context and service parameters
Add tests for @Parameter injection mechanism

We want to make sure that *any* class which has @Parameters of type
org.scijava.service.Service or org.scijava.Context has those parameters
populated with the context's associated values, when
Context#inject(Object) is called on it. We also want to make sure that
*if* the object implements the Contextual interface, the result is
exactly the same when calling Contextual#setContext(Context).