Add new register phase

[peverwhee]

Tag name (required for release branches):
Originator(s): peverwhee

Description (include the issue title, and the keyword ['closes', 'fixes', 'resolves'] followed by the issue number):

1. Adds call to new CCPP register phase brought in with framework PR #582
2. Uses the full error message returned from the exception handled when xmllint is called (updated in framework PR #586)
3. Adds inverse_exner_function_wrt_surface_pressure as possible input variable name for exner for backwards compatibility with old converted snapshots

closes #215 (add optional register phase)
closes #286 (Improve error message returned by XML linter)

Describe any changes made to build system: None

Describe any changes made to the namelist: None

List any changes to the defaults for the input datasets (e.g. boundary datasets): None

List all files eliminated and why: None

List all files added and what they do: None

List all existing files that have been modified, and describe the changes:
(Helpful git command: git diff --name-status development...<your_branch_name>)

M .gitmodules

• brings in new CCPP framework tag

M src/control/cam_comp.F90
M src/physics/utils/phys_comp.F90

• Adds call to new CCPP register phase in the generated cap

M src/data/generate_registry_data.py

• Uses full error message returned from xmllint

M src/data/registry.xml

• add backwards-compatible exner name

If there are new failures (compared to the test/existing-test-failures.txt file),
have them OK'd by the gatekeeper, note them here, and add them to the file.
If there are baseline differences, include the test and the reason for the
diff. What is the nature of the change? Roundoff?

derecho/intel/aux_sima: all pass

derecho/gnu/aux_sima: all pass

If this changes climate describe any run(s) done to evaluate the new
climate in enough detail that it(they) could be reproduced: N/A

CAM-SIMA date used for the baseline comparison tests if different than latest:

[nusbaume]

Looks good! I did have a couple of requests, but they aren't required to bring this PR in. Thanks!