Fix #623 Add audio/video quality configuration support (+24 squashed commit)

Squashed commit:

[67b9df5] Minor code fix

[1565f66] Code fixes

[70fc7dd] Fixed initialization order of avWidget

[309ee85] Updated test with default values

[5bbf519] Fixed video setup bug; Quality config entry is disabled not hidden when output is disabled

[e00820a] Fixed quality combobox enabled state bugs

[ee96531] Disable quality options when no output is configurable

[842a118] Moved bitrate/quality config to separate dialog

[5814060] Added docstrings

[02028ab] Removed unnecessary variables and arguments

[bd7deb4] Changed audio/video quality at record time; Added custom field to quality

[08ad6c0] Some more efficiency improvements

[efc1f81] Modification to test

[250ea42] Fixed config test and loading of avWidget

[46b17ec] Removed config load checks for plugins that don't need it

[8fcac96] Removed redundant config loads

[8182acb] Quality disabled for non-desktop sources

[32b40a7] Moved video resolution determination to input plugins and passthrough plugin

[e40df67] Added scaling support

[f2b56d1] Added 'configurable' variable to output plugins class

[32b37e7] Some code changes

[68280fd] Add Audio/Video quality saving to config. All output plugins except WebM now affected.
Added bitrate/quality customization to Ogg Icecast.

[ad6f7c3] Ogg Output settings now modified by quality selection

[959e916] Added ComboBox for Quality selection (+4 squashed commit)

Squashed commit:

[70fc7dd] Fixed initialization order of avWidget

[309ee85] Updated test with default values

[5bbf519] Fixed video setup bug; Quality config entry is disabled not hidden when output is disabled

[e00820a] Fixed quality combobox enabled state bugs (+3 squashed commit)

Squashed commit:

[5bbf519] Fixed video setup bug; Quality config entry is disabled not hidden when output is disabled

[e00820a] Fixed quality combobox enabled state bugs

[ee96531] Disable quality options when no output is configurable (+3 squashed commit)

Squashed commit:

[ee96531] Disable quality options when no output is configurable

[842a118] Moved bitrate/quality config to separate dialog

[5814060] Added docstrings (+2 squashed commit)

Squashed commit:

[5814060] Added docstrings

[02028ab] Removed unnecessary variables and arguments (+2 squashed commit)

Squashed commit:

[bd7deb4] Changed audio/video quality at record time; Added custom field to quality

[08ad6c0] Some more efficiency improvements (+2 squashed commit)

Squashed commit:

[efc1f81] Modification to test

[250ea42] Fixed config test and loading of avWidget (+2 squashed commit)

Squashed commit:

[46b17ec] Removed config load checks for plugins that don't need it

[8fcac96] Removed redundant config loads (+2 squashed commit)

Squashed commit:

[8182acb] Quality disabled for non-desktop sources

[32b40a7] Moved video resolution determination to input plugins and passthrough plugin (+2 squashed commit)

Squashed commit:

[e40df67] Added scaling support

[f2b56d1] Added 'configurable' variable to output plugins class (+2 squashed commit)

Squashed commit:

[32b37e7] Some code changes

[68280fd] Add Audio/Video quality saving to config. All output plugins except WebM now affected.
Added bitrate/quality customization to Ogg Icecast. (+2 squashed commit)

Squashed commit:

[ad6f7c3] Ogg Output settings now modified by quality selection

[959e916] Added ComboBox for Quality selection