Add ability to load/save multiple (streaming) output configurations in a JSON file

[obinnaokechukwu]

OBS currently has default output configurations loaded from an ini config file

See docs

As proposed in RFC 27, we need to store output specific configuration in its own json file in order to have multiple outputs.
The current *.ini files will keep being used as they are today i.e. for storing default configuration.

This basically means that we first initialize the outputs with the default config and overwrite the defaults with those specified in the streaming-outputs.json configuration file.

[obinnaokechukwu]

The new JSON file should be copied when profile is copied over