Cleanup for ParserBuilder.
Character reading methods moved to a new trait.
Added Key types for both parser and processor.
Works with String.

Need to remove QName, then test with some specific Key.
Moved Element out of Launcher for clearer code.
Not completely satisfying for compiler bug reasons.
However, we now have a more complete inheritance hierarchy, for what
it's worth.
Cleaned up the code with childBuilder (i.e. elements that could in
theory build elements of a different nature.)
The added complexity did not seem to be worth it.
Cleaned up QName.
Previous commit was uncomplete.
solved bug where running with no callback caused stackoverflow (bad
builder call.)
last commit uncomplete
removed nasty bug:

trait A { type X }
trait B extends A { class X extends super.X }
trait C extends B { class X extends super.X }  //unsound

Actually, C cannot easily extend B unless X doesn't change (even simple
derivation is unsound.)
Introduced Delegates.
Now trying to get rid of Launcher and put builders on the processor top.
Version that removes all known problems in the core.