doc/radosgw: Promptify CLI, cosmetic fixes

doc/radosgw: Promptify CLI, cosmetic fixes

Use the more modern prompt block for CLI commands
and use right one $ vs #.
Fix indentation on JSON example outputs and
some CLI command switches.
Add some arguably missing comma in JSON example output.
Add a full stop at the end of a one-sentence paragraph.
Remove extra comma mid-sentence in another.
Fix missing backslashes or typo at end of multiline commands.
Lines under section headings as long as heading text.
Fix hyperlinks. Fix list items prefixed with - insted of *.
Format configuration syntax in the middle of text as code.
Fix typo "PI" to "API" and remove extra space.
Remove colons at the end of section headers in a few places.
Use Title Case in section titles consistently with short words lowercase.
Possibly controversial: don't add whitespace before and
after main title section header text.
Possibly controversial: don't indent line continuation
backslashes, leave only 1 space before them.

Signed-off-by: Ville Ojamo <14869000+bluikko@users.noreply.github.com>