Optimize second step of LUniv

Use List.forall instead of Set.--
Time reduction up to 10x
Removed unoptimized LUniv
Removed NodeKind type
Many optimization tries for LUniv
Cleanup LUniv after optimization
Merge branch 'master' into develop

* master:
  sbt and maven used together as it should be. This couple is no brainer, just do each time you modify build.sbt 1) sbt make-pom 2) cp target/scala-2.10/skeptik_2.10-0.2-SNAPSHOT.pom pom.xml and don't forget to commit pom.xml
Remove comment saying that BuildHive status was wrong
Merge branch 'hotfix/0.1.3' into develop
Fix SBT warning about multiple resolvers with the same name.
BUGFIX: don't lower if the dual is in Delta

If Delta contains both a literal and its dual, the proof after deletion
is inconsistant. This might result in proof bigger than with LU (4%) or
proof with wrong conclusion (0.5%).
Alternative (non-working) LUniv algorithm
BUGFIX: valent literal must be in the conclusion
BUGFIX: valent literals must be in the conclusion
Merge remote branch 'origin/feature/fastLUniv' into fastLUniv

Conflicts:
	src/main/scala/at/logic/skeptik/algorithm/compressor/combinedRPILU/LowerUnivalents.scala
Merge commit '37e456f90a78b2a507c32820bae912c52bdad3f2' into feature/paper

* commit '37e456f90a78b2a507c32820bae912c52bdad3f2':
  fix hbox overful
  Algorithm's name in texttt
Add a missing dot in the conclusion of the paper
Qualify the "compression/duration differences" as "normalized"
Merge branch 'feature/paper' into develop

Conflicts:
	project/plugins.sbt
Merge branch 'fastLUniv'