Added booleanManifest to Const object
Added some optimizations for if-then-else expressions, in the cases that one of the branche is a constant true or false)
Changed Scala code generation for boolean OR and AND expressions
+ Added optimizations for Ordering operations (but as comment, because I was not sure whether they would really help. For the cases that an Ordering operation and its negation are both used in a program, these optimizations would not pay off)