Demo a flag-based tooling parser

[Pike]

Stas, this would be a feedback? in old bugzilla days ;-)

A very rudimentary start at a syntax-detecting tooling parser.

I tested it locally against

# Foo
foo =  bar

[[joe]]
bar = hi

and master parses a GroupComment and this branch gives a Junk for the [[joe]] line.

Questions:
Is this something you'd like me to spend time on?
I chose a separation between features and syntaxes, to make the code easier to understand, but also pave the way for future versions where there's overlap between syntaxes. Does that make sense?

[stasm]

With #107 merged, this PR can be closed. We ended up removing the support for old syntax from the parser and thus not having to implement the flag-based approach.