Add support to invoke arch-audit with alternative parameters

[mingue]

Currently, the application doesn't allow to specify some of the parameters when invoking the arch-audit binary, like dbpath.

It will be good to support removing the default -u or specifying a different DbPath.
I use btrfs with snapshots and don't take snapshots from /var so I moved the pacman DB to a different location.

I can submit a patch, if the project is still alive