Modified the project structure, removed module extension and went instead for a non-complete core dependency graph

Semi-encapsulated the core/api dependency graphs and created a proper structure to load eager singletons

When more than one invitation socket is opened, Alice should pick which one to use and Bob should use whichever one Alice picks. This fixes a race condition where each party picked a different socket and closed the other.

This avoids a potential problem where the app crashes after adding the contact but before adding the transport keys, leaving the contact unusable.

The polling interval increases exponentially each time polling is unsuccessful, up to a maximum of 60 minutes. The interval is reset to 2 minutes whenever a connection is made and whenever Bluetooth is re-enabled.