Fix #1345 by not calling the callbacks from InteractiveParser.accepts

[MegaIng]

This also has the nice benefit of making accepts faster since it does less work. Technically this is an option that an end user can access on their instance of InteractiveParser, so I added a bit of documentation.

[erezsh]

I wonder if instead of having to add a new parameter on all these methods, we can instead clear the callbacks on the copy method which accepts() uses. Like new_cursor = self.copy(callbacks = {}).

Then all we need is to change in the parser is value = callbacks[rule](s) if callbacks else s

It's a bit more implicit, but it feels cleaner to me. What do you think?

[MegaIng]

We are currently avoiding creating a copy of the ParserConf object since it's semantically immutable. So we have to either:

• create a deepcopy in accepts (very expensive)
• always copying ParserConf in the normal __copy__ (unnessary, although it wouldn't be that expensive)
• create an extra set of methods on InteractiveParser, ParserState (and maybe ParserConf) just for this usecase that specifcally doesn't copy callbacks
• specifically make a copy of ParserConf after doing a normal copy of InteractiveParser. (Not sure if I like this)
  • Although, I guess we could create a single copy of ParserConf in accepts and use that for all Tokens...

[erezsh]

An alternative implementation has been merged.