start to move and refactor some stuff

src/main/scala/leon/purescala/LikelyEq.scala

src/main/scala/leon/purescala/TreeOps.scala

src/main/scala/leon/synthesis/ArithmeticNormalization.scala

src/main/scala/leon/synthesis/rules/IntegerEquation.scala

...main/scala/leon/synthesis/rules/IntegerInequalities.scala

src/test/scala/leon/test/PureScalaPrograms.scala

src/test/scala/leon/test/purescala/LikelyEqSuite.scala

src/test/scala/leon/test/purescala/TreeOpsTests.scala

...la/leon/test/synthesis/ArithmeticNormalizationSuite.scala

...test/scala/leon/test/synthesis/LinearEquationsSuite.scala