(User manual) Add information about the security of the backup database

[MaplesThroughWindows]

Missing feature

There is no mention in the User Manual of how the backup database is secured at rest (Moolticute issue #1004).

Justification

Users will be justifiably relieved to know that that the backup database is secured at rest, and how it is secured. Simple things like this can easily go overlooked on a project and users need to be explicitly reassured that the devs have addressed this.

Workarounds

Had to open an issue and ask :)