DA gen_be_v3 updates for cv_options=5 etc (#1276)

[hsbadr]

TYPE: enhancement

KEYWORDS: WRFDA, gen_be_v3, cv_options=5

SOURCE: Jamie Bresch (NCAR)

DESCRIPTION OF CHANGES:
A collection of fixes and enhancements for gen_be_v3

1. add multi-variate statistics capability for stream function, velocity potential, temperature and surface pressure
2. bug fix for be_method=ENS with multiple valid dates
3. add time_lag_ens option for calculating statistics from time lagged ensembles
4. add a sample makefile that uses WRFDA-compiled lapack-lib.

LIST OF MODIFIED FILES:
M var/gen_be_v3/README.gen_be_v3
D var/gen_be_v3/compile_casper
D var/gen_be_v3/compile_cheyenne
M var/gen_be_v3/gen_be_v3.F90
A var/gen_be_v3/makefile
A var/gen_be_v3/util/combine_be_cv5.f90
A var/gen_be_v3/util/makefile

TESTS CONDUCTED:

1. The updated code has been used by Taiwan's Central Weather Bureau and NCAR's Antarctic Mesoscale Prediction System.
2. Jenkins tests all passed.

RELEASE NOTE: WRFDA gen_be_v3 is updated for cv_options=5 and ensemble applications. Please see var/gen_be_v3/README.gen_be_v3.

The first line should be a single-line "purpose" for this change

TYPE: choose one of [bug fix, enhancement, new feature, feature removed, no impact, text only]

KEYWORDS: 5 to 10 words related to commit, separated by commas

SOURCE: Either "developer's name (affiliation)" .XOR. "internal" for a WRF Dev committee member

DESCRIPTION OF CHANGES:
Problem:
Generally or specifically, what was wrong and needed to be addressed?

Solution:
What was down algorithmically and in the source code to address the problem?

ISSUE: For use when this PR closes an issue.
Fixes wrf-model#123

LIST OF MODIFIED FILES: list of changed files (use git diff --name-status master to get formatted list)

TESTS CONDUCTED:

1. Do mods fix problem? How can that be demonstrated, and was that test conducted?
2. Are the Jenkins tests all passing?

RELEASE NOTE: Include a stand-alone message suitable for the inclusion in the minor and annual releases. A publication citation is appropriate.