umxCLPM refactor and corrections

[lf-araujo]

Major refactor of umxCLPM which:

• corrects specifications of the three models
• includes some optional pre-post-processing (threshold fixing, scaling)
• WLS estimation
• seamless inclusion of definition variables
• brand-new test units
• tabs
• follows package style

This is the result of at least a year of testing, passes local tests too.

[tbates]

Looks great! Thanks for the clear message too. T