Add tests for Context creation with services

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).