Remove `HoverAspect` and `IScalaWordFinder`

I'm not entirely sure if the removal of `HoverAspect` doesn't break
anything. It is definitely not used in Scala hovers, because the Scala
IDE has its own implementations. It may be used by some Java hovers, but
I couldn't find one that actually uses it. In the worst case this change
means that some Scala elements are no longer shown in Java hovers.
Conflicts:
	org.scala-ide.sdt.core/src/org/scalaide/util/internal/ScalaWordFinder.scala
Merge pull request #814 from huitseeker/793-reissue

Remove aspect hover