Revise RFC file layout to improve workflow for linking to RFC's.

This commit just:

* combines the `complete/` and `active/` directories into one: `text/`

* renames all of the RFC text files to use their earliest associated
  PR number as the RFC number.

A follow-on commit encodes the `active`/`complete` distinction into a
list in the README.md file, and fixes a few mistakes in the RFC files
that I encountered along the way.
Fixed typos and format inconsistencies in headers of various RFCs.

In particular:

* The RFC associated with #127 should have had a link to #19 as well
  (and has been assigned RFC #19); it also was revised to match the
  markdown href style of other RFCs.

* RFC #34 needed its header entries filled in,

* RFC #123 had a typo in its header, and

* RC #155 was revised to match the markdown href style of other RFCs.
Revised README.md to contain a list of the active RFCs.

Added a table-of-contents in the hopes that will ease navigation: the
document now starts off with the active list after the introduction,
so I anticipate that one will not see as much of the expository text
as one used to, and thus the table of contents will help someone who
is skimming to find their objective.
Update RFC Process document with procedure one follows with new dir layout.
Merge pull request #367 from pnkfelix/fsk-revise-file-names-and-dir-layout-for-issue-360

Revise file names and dir layout for issue 360