Fix #664 Feedback when desktop record region selected
Skip tests related to RTMP plugin for Windows

The RTMP plugin is not included in GStreamer for Win32, so the test based on it will fail on Windows.
The workaround is to skip the RTMP test on Windows.
Updates to http errors, and validation

Changed HTTPError class to have more standard error messages, and
custom inner descriptions.

Decoupled JSON Schemas from validate module, now schemas are either
generated by config classes, or stored statically in the api blueprint.

Added JSON validation schemas to recording api Blueprint

Updated validation tests for validate.py changes, changed xunit setups
to pytest fixtures
Added ComboBox for Quality selection
Ogg Output settings now modified by quality selection
Add Audio/Video quality saving to config. All output plugins except WebM now affected.
Added bitrate/quality customization to Ogg Icecast.
Some code changes
Added 'configurable' variable to output plugins class
Added scaling support
Moved video resolution determination to input plugins and passthrough plugin
Quality disabled for non-desktop sources
Removed redundant config loads
Removed config load checks for plugins that don't need it
Fixed config test and loading of avWidget
Modification to test
Some more efficiency improvements
Changed audio/video quality at record time; Added custom field to quality
Removed unnecessary variables and arguments
Added docstrings
Moved bitrate/quality config to separate dialog