Updated the server-side encryption documentation.
- Reorganized and streamlined
- Improved clarity throughout
- Fixed a few outdated comments/notes
- Additional reference links
- Added context of "encryption" to help reader understand SSE in the context of other encryption solutions (both within Nextcloud and provided by their OS/etc)
- Expanded/clarified key management modes and encryption methods a bit
Signed-off-by: Josh <josh.t.richards@gmail.com>