KDL 2.0: identifier-based quoteless strings

[zkat]

I thought a lot about this (and we've talked about this at length in #308, but I think we should just do it, and that it's going to be ok. In practice, there will be ways to catch typos in a reasonable way, and I think quoteless strings (following identifier syntax) are actually a huge UX improvement for human-authored/maintained configuration files.

Feel free to protest this change here, or up/downvote with reactji, but I'm now leaning towards this being a major KDL 2.0 change.

[larsgw]

I think this, especially when combined with #340, can be very confusing. Of course a good linter can prevent such confusion. E.g.

ident ident ident          =ident

Or

ident ident = ident ident

[zkat]

After thinking about it I think I'm going to withdraw this. I have an alternative proposal.

[zkat]

After conversation in #350, it looks like this is what we're gonna go with after all...

[zkat]

This has been merged into the kdl-v2 branch