Spaces in Encoding Profile arguments cause errors

Problem: Some FFmpeg filters require spaces in the filter configuration. Unfortunately, spaces don't work well with Matterhorn as it tries to split the filter definition and send them to FFmpeg as a list of arguments rather than a single argument.

Possible solutions:

• Make the argument parser of Matterhorn more “intellgent”

• Introduce a space-placeholder

• Let the user set the FFmpeg command in a way that can easily be parsed (e.g. a JSON array)