Generate "SQS" with a target order parameter

It seems that SQS are quite widely used so we are perhaps not utilizing their full potential yet.

In that regard having a way to generate structures with a target order parameter could be useful.

For a binary generating a SQS with 0 to 1 with 0.1 increments in order parameter could then be used to analyze what effect of ordering could have on other properties without having to to CE construction and MC simulations

Suggestion

• add a target_sro which is a float for a binary but eg list of SRO_A-B, SRO-A-C, SRO_B-C for a ternary