improve abs xtext hovering info

currently the hovering info in the abs xtext editor is quite basic (cf. screenshot)

it would be useful to also display additional information such as:

• on assettype/asset: name of the DefinitionGroup/AssetGroup which contains the defition (useful in case the file use the with statement
• an overview of the available properties and references
• display the associated descriptions/documention
• if available use user preferred language (cf. #290 (closed))
• Use -nl option when launching eclipse
• use an overrided locale specified in the eclipse preference