Fast eddy microphysics clean up

[nataraj2]

This PR cleans up the FastEddy microphysics. The workflow for the FastEddy case is as follows

1. prob.cpp initializes rhoQ1 and rhoQ2 - i.e. rhoqv and rhoqc.
2. rhoQ1 and rhoQ2 are advected.
3. Init_FE.cpp defines micvars qv and qc from rhoQ1 and rhoQ2 (dividing by rho)
4. FastEddy.cpp updates qv, qc and theta - condensation and evaporation (no precipitation)
5. Diagnose_FE.cpp is empty - we solve for qv and qc - nothing to be diagnosed.
6. Update_FE.cpp updates rhoTheta, rhoQ1 (i.e. rhoqv) and rhoQ2 (i.e. rhoqc) using the updated values in step 4.