JBIDE-15645: revisit stacks archetype management

- reads a new stacksType attribute from project-example*.xml
- falls back on previous behavior when stacksType is missing
- dynamically switches between archetype versions of same
  stacksType, based on selected  runtime/ blank flag. Allows for
  different archetype GAVS between community/product and between
  different JavaEE environments
- The best matching archetype version is selected, when an exact
  match can't be found
- adds additional repositories to ConfigureMavenRepositoriesWizard,
  extracted from stacks.yaml, per archetype version
- checks for essential dependencies defined per archetype version
  in stacks.yaml
- added mockito jars for as test dependencies.

Signed-off-by: Fred Bricon <fbricon@gmail.com>
JBIDE-15499 - Support drag'n'drop of links to 'connectors' similar to marketplace to central for auto install