Removed support for boolean from type system

Does not seem to be worth it.
Also, at the moment, I am using implicit casts from SOM objects to Java primitive types, but there is no simple cast and check for booleans, since they are just normal objects and not builtin types.
The interpreter gets a little faster again after removing the booleans.
[TODO-REPORT: tradeoffs, complexity, speed, expected gain]

Signed-off-by: Stefan Marr <git@stefan-marr.de>