updating and cleaning up new udm microphysics for optimization

[dudhia]

TYPE: enhancement updates, optimization fix

KEYWORDS: microphysics constants and process update

SOURCE: Songyou Hong via internal

DESCRIPTION OF CHANGES:
Problem:
Previous code did not compile with intel -O3. Also changes to constants and process which are updates.

Solution:
Minor change allows optimized compile. New code performs more as expected and is cleaned up.

ISSUE: none

LIST OF MODIFIED FILES:
M dyn_em/solve_em.F
M phys/module_microphysics_driver.F
M phys/module_mp_udm.F
M phys/module_physics_init.F

TESTS CONDUCTED:

1. compiles
2. tested with 2d squall line case
3. still need to test bit-for-bit

RELEASE NOTE: updates to new UDM mp scheme from developer.

[dudhia]

In addition to checking what happened with regtest, need to do bit-for-bit test with mp_physics=27