Add groupId and artifactId to UI including validation (partly #274, #149, #150)

[geziefer]

Enhance UI with two input fields for group and artifact id (layouted in 1 line to save space). Both values are validated to java package naming convention and jar naming convention, respectively. Validation messages appear for both empty and illegal field values on top of the form, both when pressing the button or when leaving the field. Button works directly from field as well as when having selected something else before. Version was explicitely not regarded, as this can easily changed by the user and is seldomly useful to set at the beginning after creating a project template to anything else. Plus, the validation here would be different as the there are conventions, but the user could use something else as this has no effects on the generated files. The archetype is fed with the new values or defaults are used if unchanged. Only with the defaults caching happens as with individual values this would not make much sense as it is very unlikely to hit the cache if the values are freely set. Was tested alone and in combination with the other PR using the artifactId in all files.

[eclipse-starter-bot]

Can one of the admins verify this patch?

[m-reza-rahman]

Is this ready for serious review yet or should I wait a bit more?

[geziefer]

@m-reza-rahman Yes, it should be. This part is pretty much what I did before, including full validation. I tested the UI for different szenarios and the result looked good to me.