Infeasibiity due to allow_startup_shutdown_power

[sriharid]

A parameter named allow_startup_shutdown_power introduced in the opchar table in v0.15.0 can result in an infeasibility. Setting this parameter to 0, which is also its default value, could result in an infeasibility since max_shutdown_power_constraint_rule (which only allows Provide_Power_Shutdown_MW = 0) is incompatible with ramp_during_shutdown_constraint_rule (which enforces the Shutdown_Ramp_Rate_MW_Per_Tmp).

[sriharid]

It would help the user if validation catches the case where the allow_startup_shutdown parameter flag is not set, but startup or shutdown parameters are provided. The severity level of the validation error can be High since it could result in an infeasibility.