adding some logging to field add
new init routine for time step
moving test to a function
storing number of subdomains and fields in time step
slightly modifying function handle interface
filling out the test function handles
fixing dummy rate calculation
warning message
removing type warning and init fields to zero
Starting to handle LSRK step.

TODO:
Commmunicator, fix function pointers (inter/intra), update test with multiple
domains.