Migration from INI to YAML

[hatkidchan]

Using INI as configuration format adds a lot of headaches. The only reason post_init exists on filters is because we can't load all filters immediately. Using YAML would solve pretty much all of the configuration problems, as well as may allow for multiple sources to be used simultaneously within one file. Plus, it makes usage of filters and integrations more explicit.

The only downside I see is that we can no longer use same filter in multiple output modules, as well as we can't use variables from one module in another. That, however, can be solved by creation of shared filters and variables.

The other option is to fucking fix current configuration loader which should've been done a while ago.

[CyberTailor]

YAML is the most complicated file format in the universe. Seems like overkill.