Add self-secret option

What's New

• Add -x, --self-secret option to make secret unreadable to other than the UID user.

First covert release

What's New

• Secret versioning with covert commit
• Automatic secret rotation in service with covert update
• User controllable secret file permission (UID, GID, Mode) on covert add/update
• Secret versioning one-line type cleanup with covert cleanup