Update property-types test case with more realistic types.
Improvements to generated code for generic property types.

Note that method call 'equalTo(x)' where x is a Box<? extends Widget>)
returns a matcher of type
Matcher<? extends Box<? extends Widget>> by default. This is
undesirable, as it can't then be assigned to a PropertyMatcher that
accepts Matcher<? super Box<? extends Widget>>. This problem can be
avoided by explicitly stating the type, as in:
CoreMatcher.<Box<? extends Widget>>equalTo(x).

This is only necessary when the type of x includes a wildcard at the top
level. If x has type <Box<Box<? extends Widget>> then the return type
is Matcher<Box<Box<? extends Widget>>>, which is fine.
Change structure of generated code for extensible matcher to include a
nested class and static factory methods in all cases.
Initial data for test case for generic type matcher.
Partial implementation of generics matcher generation.
Add TypeBuilder constant for 'void' type.
Add matchesSafely method to generated matchers.
Extend generator to support matchers of generic types.
Fix issue with generated matchesSafely method.

The call to super in MatchesSafely does not type-check for extensible
matchers when the method is overridden in the main class. This change moves
the method into the nested class.
Remove the concrete subclass name parameter from the generator properties
and the options dialog.

The generator has been changed to always generate a concrete subclass as
a nested class in all extensible matchers.
Add test case for generating matcher for leaf of class hierarchy.

When generating a matcher for a subclass without specifying any superclass
matcher, all properties on the class hierarchy are included in the matcher.
Add test cases for testing generation of non-extensible and extensible
matcher subclasses.
Add test case and support for generating subclass matchers for generic
types.
Fix @Matches annotation on generated matchers to use imported class instead
of fully qualified name.
Add test case for testing generation of extensible subclass matchers (i.e.
matchers that extend other matchers) for generic matched types with generic
superclasses.
Update documentation for new release 0.2.
Update plugin metadata with appropriate minimum IDE version requirement