Initialization and users app

[dboulware]

This PR:

• Introduces an initialization app that ensures the sensor capabilities, calibrations, switches, preselector, sensor, and signal analyzer are initialized in the correct order and available to the other Django applications through singleton classes.
• Replaces the create_superuser script with a users app that initializes the users. This is to eliminate unnecessarily creating the django app multiple times.
• Removes the migration_setting and runtime_settings and instead uses a single settings file, but checks within the code if migrations are being run to avoid connecting to the signal analyzer while migrations are being run.
• Adds an optional USB_DEVICE and adds usbutils to the api container to allow the scos-sensor to check for a required usb device. If the device is not found it will restart the container.
• Checks the signal analyzer if it is healthy on startup and restart the container if the signal analyzer is not healty.
• Adds /dev/bus/usb as a volume in the container. This was done in hopes that it would allow the container to see the signal analyzer even when the container started before the USB was ready. It doesn't appear to do that, but it looks like it changes the usb error to a recoverable error.

[aromanielloNTIA]

Looks good and works well based on testing on seadog01. See a few comments about defaults inline below.