Implemented a first version of the naive subsumption algorithm

I also created a test proof which shows the desired behaviour.
Relates to Issue #63
Implement suggested changes and add ForwardSubsumption to CLI
Make axioms subsumable and replace name ForwardSubsumption by FWS
Implement first version of RecycleUnits
Merge remote-tracking branch 'upstream/develop' into develop
Implement second version of RecycleUnits and a test for this algorithm.
Add RecycleUnits to CLI.
Implement BackwardSubsumption and intermediate RecyclePivot algorithms

Add both to CLI and include testcases for BackwardSubsumption
Merge remote-tracking branch 'upstream/develop' into develop

Conflicts:
	src/main/scala/at/logic/skeptik/algorithm/compressor/package.scala
Remove reference fixedPremise, merge with main repository
Implement BWSm and rename old BWS to BWSt
Use bottomUp traversal in check of ancestor in the BWSm algorithm
Merge remote-tracking branch 'upstream/develop' into develop
Merge remote-tracking branch 'afellner/develop' into correction2
Add existsAmongAncestors method to ProofNode
Improve existsAmongAncestors for speed
Merge remote-tracking branch 'existsAA/feature/existsAA' into develop
Implement suggested changes in BWSt
Merge commit '9eea83fe85ab000163482ea872825a1914fd6721' into develop

* commit '9eea83fe85ab000163482ea872825a1914fd6721':
  Implement suggested changes in BWSt
  Improve existsAmongAncestors for speed
  Add existsAmongAncestors method to ProofNode
  Use bottomUp traversal in check of ancestor in the BWSm algorithm
  Implement BWSm and rename old BWS to BWSt
  Remove reference fixedPremise, merge with main repository
  Implement BackwardSubsumption and intermediate RecyclePivot algorithms
  Implement second version of RecycleUnits and a test for this algorithm. Add RecycleUnits to CLI.
  Implement first version of RecycleUnits
  Make axioms subsumable and replace name ForwardSubsumption by FWS
  Implement suggested changes and add ForwardSubsumption to CLI
  Implemented a first version of the naive subsumption algorithm

Conflicts:
	src/main/scala/at/logic/skeptik/algorithm/compressor/package.scala