Removing all unsafe casts

- some of them are there to provide more definite type info
- and most of them to indicate the guarantee of a value being not null
There are removed because they should not be necessary, and will probably be removed from Graal entirely eventually

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

Conflicts:
	src/som/interpreter/nodes/ContextualNode.java
Remove optimizations for globals

- needed to put in bool objects into globals table, because, actually, we do not support Boolean objects anymore. Oops...

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

This version doesn't need to optimize the unknown globals handler, but at least it should not prevent compilation completely.

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