Fix #623 - Add Quality selection options to ConfigTool for Audio/Video output

Fix #623. Easier configuration for output quality of video and audio by using a combo box to select. The bitrate determined for video will be based on the system resolution.

Tasks:
- [x] Add ComboBoxes for quality selection
- [x] Have ComboBox selection set qualities for Ogg Output
- [x] Have ComboBox selection set qualities for all plugins
- [x] Save ComboBox selection in profile and whether it should be used or has been overridden by manual quality entry
- [x] Add config support for Ogg Icecast
- [x] Disable config button and quality comboboxes when RAW or WebM Output is selected
- [x] Support scaling
- [x] Support non-screen inputs (NOT POSSIBLE)
- [x] Recompute video bitrate based on quality and resolution on record if "No Scaling"

Screen:
![quality selection](https://cloud.githubusercontent.com/assets/5759678/4958137/1ff74286-66ab-11e4-85b9-a0fe68cb225b.png)
This code for checking if the config is loaded is repeated a lot. Consider adding a `get_config()` or similar that loads it if not already loaded.