Per Amazon's product page [1], S3 is officially called "Amazon S3". The
restic project uses the phrase "AWS S3" in some places. This patch
corrects the product name.
[1]:https://aws.amazon.com/s3/
This commit refactors the documentation according to my proposal in #1273
and the discussion I had with fd0 on IRC.
The bits from the manual that I could not immediately put into the new
structure are contained in manual_rest.rst Anything else is still there,
nothing has been deleted.
I changed the heading markup to follow the convention used in Python’s
Style Guide for documentation, this convention is explained in a comment
at the top of every file.
I also added a paragraph on installing restic on Debian.
