We want to create a new config file that is shared across the different libraries and tools that use the gridscale API: gridscale/terraform-provider-gridscale#183

For this we need to have a function that reads that config file into an internal representation and probably also a function that writes such a config file if it does not yet exists.

See gridscale/terraform-provider-gridscale#183 for the format of the file and file paths on the different platforms.