Support for remote resizing to match client resolution

[danisla]

Make sure to clone the repository with the --recurse submodules flag to bring in all of the submodules.

git clone --recurse-submodules https://github.com/selkies-project/selkies-vdi.git

New features:

• Support for matching the remote resolution with that of the web client.
• Both the software x264 and hardware nvenc encoders are supported.
• Toggle remote scaling from webrtc web interface side panel. Default is enabled.
• Toggle local scaling from webrtc web interface side panel. Default is disabled.
• Set default remote resizing from the BrokerAppConfig appEnv WEBRTC_ENABLE_RESIZE set this to true or false.

Limitations:

• The maximum width and height for the remote is 2560x1600 with NVENC and 4096x2160 with the software x264 encoder.

General Improvements:

• Imported all gst-web lib dependencies into the repo.
• Imported guacamole client standalone Keyboard module.
• Parameterized the watchdog image, so it can be set from the BrokerAppConfig.

Bug fixes:

• Fix issue where input control is lost when reconnecting.
• Fix keyboard repeat issue with WebRTC.