Implement usbguard-oneshot component

[dkopecek]

Some users may prefer not to run an additional daemon for various reasons:

• their USB device usage policy doesn't need to be dynamic (no user interaction, fully defined by a static rule set)
• minimize always running components on the system
• low USB device "traffic" (i.e. using a USB device once a month, etc.)

A "oneshot" component which would be triggered on-demand (by the user, via a udev rule) would load rules, apply them on devices currently connected to the system and exit.