Split the spec into two

[solderpunk]

On Tue, May 26, 2020 at 10:12:26PM +0200, Felix Queißner wrote:
 
> > I still think it's a good idea to have everything in one place, but some
> > rearrangement would not hurt.  I will try to do this tonight.
> Nice, thanks!

I just made this change, moving the definition of text/gemini into its
own section at the end of the spec (but before the appendix listing all
status codes), so that all of the protocol stuff is contiguous.

While I was at it, I fixed the ridiculous section numbering scheme.
Literally everything was a subsection of a single top-level section!
Talk about nuts.  So most things that were 1.x.y.z became just x.y.z.
All the text/gemini stuff got moved to its own dedicated section 5, so
the deepest level of nesting is also now one level less than it was
before.

This is a big overall improvement in readability and citeability.
Thanks a lot for suggesting it.

Cheers,
Solderpunk