Adding support for normalized serotypes, different output

Now it's possible to normalize introductions by number of serotypes, i.e. the
number of introductions can be invariant to whether 1, 2, or 3 serotypes are
circulating.

Also, new command line flags allow users to specify daily, weekly, monthly, or
yearly aggregated output.  Output includes number of introductions, autochthonous
transmissions, and total infections in the time period.
Refactoring/synchronizing mpi_driver.h/mpi_simulator.h
Bringing vaccine/main.cpp up to date

Switching to default (precipitation-driven) mosquito model and new parameter
names.
simulator function definitions moved into a header file

driver.cpp is now very simple.  Reasonably generic functions should go in
simulator.h so they can be called from different scopes (e.g. abc, or driver).