#36 Refactor selectable lists to make the API more close to Groovy's List API.

[Jürgen Kellerer]

Selectable lists have some extensions over standard list implementations that are similar to the extensions that can be found in Groovy's List API. In order to avoid that one needs to have too many different approaches in mind the API should reuse the naming and syntax of the Groovy API where possible (e.g. plus and minus, instead of append and remove).

[Jürgen Kellerer]

Additions to the list API that were made after 1.1 will simply be refactored. Any remaining parts may be depreciated instead.