Expand test coverage for compatibility changes related to annotations

[guillermocalvo]

I updated test classes CtClassBuilder, CtMethodBuilder and CtFieldBuilder so that tests can create annotations with elements.

Example:

// Creates a test class with an empty annotation:
//     @MyAnnotation
//     class Test { }
CtClassBuilder.create().name("japicmp.Test").withAnnotation("japicmp.MyAnnotation");

// Creates a test class with an annotation that contains one element:
//     @MyAnnotation(foo = 1000)
//     class Test { }
CtClassBuilder.create().name("japicmp.Test").withAnnotation("japicmp.MyAnnotation", new CtElement("foo", 1000));

This allows for test scenarios where compatibility change ANNOTATION_MODIFIED should be reported.

Closes #385

[siom79]

Thank you for the PR.