BaseApp does all the heavy-lifting related to creating the redux store,
navigation, and so on.
App currently handles URL props and actually triggering navigation based on
them.
Move it away from AbstractApp into an auxiliary function. In addition, introduce
a new `getServerURL` function which gets the configured server URL and defaults
to meet.jit.si as before.
Saúl Ibarra Corretgé
Bettenbuk Zoltan
Lyubo Marinov