Added task for removing netbeans-generated manifest file
Reactive Lookups

Signal sources are now not only awailable for `PureLookup`s but for
all `Lookup`s in general via an implicit pimp. This can be imported
using import efa.nb.lookup._
New TopComponent subclass for reactive components

ReactiveTc automatically starts a reactive behavior (using
efa.nb.NbSystem as the reactive system) upon opening and shuts
everything down after closing the TopComponent.