Also changed from getting the local IP address to just using 0.0.0.0, which
seems to work too.

Apparently it's not supported on Windows when using IPv6.

This would influence all socket timeouts on all network connections we do,
which is a bad idea.

This is required to run pyinstaller.

This prevents the variables used there from leaking into the module-global
scope.

We're just going to distribute pyinstaller directories. These are quite a
bit bigger, but much easier to install & run.

It also needs to be extended to include the system integration files.

Some machines cause a PermissionError when sending to IPv6, but if IPv4
still works fine we should just use that instead. This change counts the
number of failed address families, and only if all of them fail we stop
the discovery.

This makes it easier to enable debug logging, as it doesn't require editing
`flamenco-worker.cfg`.

This is now also the new default, since we can't provide a sane default URL
anyway.

WARNING: this can cause duplicate worker information in the Manager's
database.

This makes it easier to re-register workers; now this can be used, rather
than editing ~/.flamenco-worker.cfg. Since that file is likely to have been
created by the Worker itself, the user may not even know it exists.