More robust and modular parse_results()

[famuvie]

This function retrieves results from several separate sections (fixed and random effects, variance components, functions of variances, goodness of fit, reml algorithm). Currently (0.11-1) if something fails, the function fails, and nothing can be retrieved.

It would be better to report a problem in the given section, and try to continue if possible.

• Write separate parsers for each section
• Write unit tests for each of them
• try() them from parse_results() and catch errors