make colored output optional, and have it changeable via cmd in Debugger

[meisl]

Performance isn't really amazing already (#10), and going through hoops to filter out color afterwards (on Windows) is for sure only adding up to the perf problem.

So, depending on what's gonna be the default, either

use Grammar::Tracer:color<True>;

or

use Grammar::Tracer:color<False>;

and same for Debugger, of course (w/out code-dupe, see #7...).

Btw, I'd say 👍 for default False.

Additionally, in Debugger there should be a command to switch it on or off at runtime.