Type safe lookup pimps

Finally got around to make netbeans Lookups type safe from a
scala point of view. It is only allowed to retrieve values from
a lookup, whose type is unaffected by erasure. This is checked
at compile time using a macro.
Renamed Lookupable to Unerased

Inspection of project nb showed that type unaffected by erasure
also play an important role in user interfaces (Properties), where
Class[A] is used to cast objects of type A. Therefore the type class
was renamed to 'Unerased'.