Improve usability when reading packages over a network share

[cohaereo]

A big improvement we can make is moving the tag cache from quicktag's directory, though for network shares we have a few smaller things to tackle

1. Generating a new cache over network should be avoided. When a network cache gets invalidated we should prompt before trying to generate a new cache
2. Copying the cache from the network is probably a good idea. We can add a hash/timestamp to the file if needed to check for changes so it can be re-copied automatically
3. How do we even detect that we're on a network share
4. ???

[nblockbuster]

3. How do we even detect that we're on a network share

On Windows, it looks like calling GetDriveTypeW on the root drive path/letter if it's a network share that's mapped to a drive letter would work. If it isn't, then checking if the path starts with \\ would probably work.