Removed StringEscape
Removed z3 and other windows executables from the git index.

Fix semantics for substring
Simpler values for enumeration, externalised special values to disambiguation.
Removed the previous reference to leon.lang.string
Removed unused and redundant code.

Conflicts:
	src/main/scala/leon/xlang/ImperativeCodeElimination.scala

Improve equality to detect equalities between literals

- InputSplit splits by a boolean input variable

- IndependentSplit splits output variables that are unrelated

Added Either in Leon Library. Fixed some code gen issues in Windows.

Conflicts:
	src/main/scala/leon/frontends/scalac/CodeExtraction.scala
	src/main/scala/leon/purescala/TypeOps.scala
	src/main/scala/leon/solvers/z3/AbstractZ3Solver.scala

Distinct cases when adding examples.
QuestionBuilder possibility to keep empty alternatives.
Added excluded tag if VerificationReport when rendering expressions.
Better web problem for grammars.

Tuples are automatically expanded one level.