Adds support for specifying Minimum Bitrate directly in the UI instead of requiring custom settings to do so. Additionally Adaptive I/B-Frames are now only shown if Look-Ahead is a value greater than 0 frames.
Quality Minimum can also now be left at a default value of -1, the Quality group is no longer toggleable and Quality Target moved into the group. Settings options on the context is now searching children too (if there are any).
Finally, some C++17 formatting was done.
Fixes#101
