Expose more Egret options in Prescient

[bknueven]

• Slack types Adding user-configurable slack type Egret#239 Adding support for specification of slack types for both RUC and SCED models #125
• PTDF Options (enumerated in Egret here: https://github.com/grid-parity-exchange/Egret/blob/d2a46cc0a2dbbd5f45dbb7a61f1cc2f6733b5929/egret/common/lazy_ptdf_utils.py#L28-L62)
• Reserve ramping constraints RTS-GMLC fixes Egret#245
• Contingency monitoring Add example 5bus case, contingency screening capability, and #128

[darrylmelander]

One way to do this generically is to add a command line option where you specify "extra" egret options.

[bknueven]

Egret options may be in one of two places:

1. In the system key of the ModelData object. Examples:
   a. reserve_ramping_constraints https://github.com/grid-parity-exchange/Egret/blob/83b371719c4141c794497c0bb89fdd320001c711/egret/model_library/unit_commitment/services.py#L423 (not currently supported in Prescient)
   b. *_price_threshold which gets converted to *_penalty_price for pricing models only. Could allow *_penalty_price to apply to non-pricing models.

2. Options for solve_unit_commitment: https://github.com/grid-parity-exchange/Egret/blob/83b371719c4141c794497c0bb89fdd320001c711/egret/models/unit_commitment.py#L1614. Could pass things through **kwargs. ptdf_options may be the most significant of these.