Restructure reading of simulation input (#188)

* first pass at moving spec file reading from partmc.F90

* fix mpi hangup

* make camp happy by passing aero_state

* move run_exact inputs

* move run_sect inputs

* add calls to spec_file_read_run for sect and exact

* move mpi calls into subroutine. move uuid4_str()

* make uuid4 call for only rank 0 process

* change spec_file_broadcast_run_part name to pmc_mpi_broadcast_run_part

* remove mpirank from spec file reading

* simplifying uuid generation