lam_sparse_ratio and lam_orthog_ratio to control default cost function weights

[tscizzlebg]

Simply allows changing the default 10% to another proportion (e.g., 20%) for lam_sparse and lam_orthog.

• Did this with optional params lam_sparse_ratio and lam_orthog_ratio.
  • Added at the end of the param list, so should be fully backward-compatible, even if someone's script is passing in parms as positional args instead of keyword args.
  • Tried to be consistent with existing code / documentation style.
• Added for both SCA and SCANonlinear.
  • Default values are .1, except for SCANonlinear's lam_orthog_ratio which defaults to 1 like it already was (and updated comment from 10% to 100% to match accordingly).

Motivation: Seems helpful/intuitive to be able to specify these cost weights relatively instead of directly, probably for the same reason the defaults are chosen that way.

[jglaser2]

Thanks! Seems like a great idea - I'll double check and merge later this week.