added age and timeSinceLast as characteristics to newborns
most basic conception function possible
most basic dissolution hazard possible
age mixing implemented in formation hazard function and cumulative hazard updated

This file gives correct distributions of formation events, with age
mixing implemented, but only works correctly if mortality and
conception/birth are switched off and if initial number of people and
number of people is the same. In a future version of this file, the
updating of the cumulative hazard will need to be modified so that it
also works correctly for populations with demographic dynamics.
extensions to accommodate age mixing rules
age scatter plot optimised
bug fixed in preparing data for exporting (line 644/654)
file for setting and changing age mixing pattern before and after age mixing intervention respectively