Scan /Applications in newly mounted partitions

[probonopd]

Instead of scanning a fixed set of locations like

• /isodevice/Applications
• /isofrom/Applications
• /run/initramfs/isoscan/Applications
• /run/archiso/img_dev/Applications
• /lib/live/mount/findiso/Applications

we should scan /Applications in every mounted partition.

This would give us support for distirbutions like Manjaro, where the Live medium is mounted at /run/miso/img_dev, without having to hardcode yet another location.

As a bonus, we should also monitor /Applications on freshly mounted partitions as they come and go (think removable drives).

@rszibele, do you want to have a go at this?

[probonopd]

I have implemented this in 660c916 but we still need to make appimaged aware of newly mounted and unmounted partitions, possibly using something like UDisks and dbus.

[probonopd]

@TheAssassin suggested just running the code that scans the mountpoints after every few seconds.

Not sure whether UDisks/dbus wouldn't be more suitable.

660c916#r31601615

[TheAssassin]

It'll surely be the better solution, but I guess periodic scanning could be used as a fallback (you could also simply combine both). I think a scanning interval of 1 min would be viable.

[probonopd]

When you attach a new disk it needs to be "instant" - or do you want to plug in a USB stick and wait for a minute?