In the else-branch of USMetarPlugin.process(), 'fromcall = fromcall'
is a self-assignment that does nothing. It was likely a leftover from
an edit that intended to reassign fromcall but forgot to write the RHS.
Remove the dead line. The variable is still used correctly on the next
line (get_aprs_fi call).
Closes#253
this patch removes the need for dacite2 package for creating
packet objects from the aprslib decoded packet dictionary.
moved the factory method from the base Packet object
to the core module.
hemna