Removed reduction from Node.java, re-implemented using IdentityHashMaps
in IntExprReduction.java
Merge branch 'master' of https://github.com/ezulkosk/Kodkod-Ints-Project

Conflicts:
	kodkod/bin/kodkod/arithmetic/ArithmeticStorageElider$Replace.class
	kodkod/bin/kodkod/arithmetic/ArithmeticStorageElider.class
	kodkod/bin/kodkod/arithmetic/EqualityFinder.class
	kodkod/bin/kodkod/arithmetic/IntExprReduction.class
	kodkod/bin/kodkod/arithmetic/Recompute.class
	kodkod/bin/kodkod/ast/Node.class
	kodkod/src/kodkod/ast/Node.java
Fixed small merge conflicts