Merge/ebocher/orbisgis beanshell

This pull request is the merge of #239 with the current master. Automatic merge was not possible anymore so we can not merge #239 directly. As I think it's quite ready, let's merge it :-)

Beanshell commands have been deleted from the OrbisGIS code. They are transformed in bsh scripts so the developer can create easily command that return an object not only a void or a string.
The user can also load custom commands using a init.bsh pushed in the workspace folder.