Config-File under Windows 10 is not searched in documented location

[dannyedel]

Under Windows 10, the configuration file is searched in /.config and not in C:/Users/NAME/.config as documented, because $HOME is empty on Windows 10 (see runtimeconfiguration.cpp +196 for the bug location).

A good solution would be to check if the (buggy) previous config file location exists and issue a warning that a user is depending on a bug.

While working on the logic anyway, #204 can be implemented alongside this, to create a list of config files and apply them in order.