detached: Theme detached-db-directory and detached-session-directory

[meliache]

• detached-db-directory is used to store the detached database and log files in plain text.
• detached-sessions-directory is used to store plain-text log-files with outputs of detached sessions.

Both directories are created automatically by detached if they don't exist yet.

By default, the detached-session-directory is in a sub-path of detached-db-directory, i.e. in my case the defaults were:

• detached-db-directory: ~/.emacs/detached/
• detached-session-directory: ~/.emacs/detached/session/

but I think that it seems more in line with the no-littering conventions to split them into different sub-paths under var/detached.

[tarsius]

Thanks!