Feature Request: Media library options for non-permanent mounts

[DeepThought]

When using external or networking devices for media storage (i.e. with your laptop) you have to rescan your library every time you mount/unmount that device. Since this is a very time-consuming action, the library should contain a feature to tell whether the device is mounted at the specified mountpoint.

If the device is not detected as mounted, those files in the library should be "inactivated" until the device is mounted again, rather than removed totally from library (thus forcing a rescan). That is: keep the information about the files in the library, but don't display them.

Additionally there should perhaps be an option to clear such information from the library, in case you move the files or just change mountpoint, thus preventing your library from being filled with non-existing, "inactivated" media files.