Add support for trait, script, etc. in New Type Wizard

[eric-milles]

JDT has separate wizards for creating classes, interfaces, etc. If GDT follows this pattern, there will be a lot of items in the New context menu. Instead, the "New Groovy Class" wizard could be enhanced to support selection of other Groovy archetypes.

It may also be nicer to have lesser-used options on the second page of the wizard. This could reduce clutter and make room for additional Groovy-specific controls.

[eric-milles]

Current work in progress:

A trait created with package visibility and self type java.lang.Number:

[eric-milles]

TODO:

1. Add controls for common AST Transforms like @Canonical, @EqualsAndHashCode, @InheritConstructors, @ToString, etc.
2. Base script should only search for types that extend groovy.lang.Script
3. Add controls for adding Inferencing Suggestions for expected script bindings
4. Remove unused or redundant imports in created type