Create a full loop of documentation for rclone about, backends overview
and individual backend pages.
Discussion:
https://github.com/rclone/rclone/pull/4774 relates
Previously pull was requested, in part, under ref
https://github.com/rclone/rclone/pull/4801
Notes:
Introduce a tentative draft see-link format the end of sections to try
rather than lots of in-para links.
Update about.go incl link to list of backends not supporting about.
In list of backends not supporting about, include link to about command
reference.
I appreciate there may be decisions to make going forward about whether
command links should be code formatted, and using proper pretty url
links, but I have fudged that for now.
Update backend pages that do not support about with wording used
previously for ftp - it is in passive voice but I can live with it. (my
own wording and fault). The note is applied to a limitations section. If
one does not already exist it is created (even if there are other
limitations with their own sections)
