Norg parser

I'm refactoring norg parser multiple times. I found that I need multiple lexers and a parser that can dynamically peek next token using different lexers. Having current token doesn't make sense because it will probably change anyways.

I'm not sure how should I structure the lexers to be that much dynamic. Maybe a parser should not hold any lexer at all and rather create them when it needs them. It can hold a Scanner and hook it into different lexers based on context, so we can share same cursor position/movement.