* Implemented the bounded variant of DeltaG.
* Restructured the Delta-vectors: 'DeltaVector' is now a trait which is implemented by its three variants (OneVariableDelta, ManyVariableDelta, UnboundedVariableDelta) in cutIntroduction/deltas.scala. The generalized delta table takes one of these as a parameter.
* Changed the signature of cutIntroG in the shell. It's now 'cutIntroG(LKProof, Constraint[Int]) : Option[LKProof]' where the 2nd parameter specifies the number of variables and is of the form NoConstraint, ExactBound(n) or UpperBound(n). If the cut introduction fails, cutIntroG returns None, otherwise Some(<the compressed proof>).

Minor changes:
* removed fol.utils.instantiateFirstN (instantiateAll is used in its stead).
* added isFunc, isVar, isFunc(FOLTerm, String => Boolean) to fol.utils.
* added overloaded versions of replaceFreeOccurenceOf to fol.utils.
* added tests for ManyVariableDelta to GrammarTests.

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@1717 85d21ef8-add0-11de-ae77-5bfb9c5a3f34