daemon: Restore the peridocially exchange of PRoPHET routing information

This mechanism is required for the propagation of transitive encounter predictions.
However, the default value has been increased from 60 seconds to 120 seconds.
daemon: Make beacon interval configurable

The option discovery_interval replaces discovery_timeout and specifies how often
discovery beacons are sent. By default every 5 seconds instead of each second. In
suspend mode, this value is increased by a factor of ten.

For incoming beacons without a timeout value, the value of the option is also considered
to define a timeout value.
daemon: Truncate unnecessary routing cycles on locally addressed incoming bundles
Merge pull request #69 from morgenroth/Efficiency-improvements

Efficiency improvements