Code revision in ILObfuscator

Guys!
Sometimes .ForEach method is very useful as it allows writing one line
of code instead of 4, and by that improves code usability making the
source code more transparent.

Andris! Possible bug: applying DeepClone to instructions in copy
constructor, their IDs are also copied. OK for now, but later we'll have
problems with XSD validation during export. Just be aware of this fact,
I'll try to solve it.