The non-themed import basically is just a proxy using some
auto-detection to find out which theme to use.
As the app only uses the basic theme, this is what we'll import.
This adds a lock to ensure that the app is not started twice, which
would be bad for data consistency.
The second version will just show a simple window stating it is already
running. While it would be nice to make it more advanced, I don't think
that is useful to spent time and code on.