Align the style for the entire documentation to prefer one sentence per
line. This has the following advantages:
- Asciidoc properly combines lines of text into a single paragraph
- This keeps the Git diff readable and minimal while keeping line
lengths reasonable
- Some Asciidoc functionnality does not interact well with hard wrapped
lines
* Update link to OSTree documentation
Specifically the one explaining the filesystem layout.
* Updated the rest of the links to ostree and rpm-ostree's docs
Both moved to GitHub from readthedocs.io, and the links referring
to specific pages return a 404 so this fixes that.
