Added a new generic model for Scalar Leptoquark productions

The model can calculate the pair productions at the next-to-leading order in QCD, and it also includes t-channel diagrams which had been ignored in previous round of Run-2 LQ searches. Furthermore, this allows to produce asymmetric and mixed generation LQ productions. The model is also available from the public link below

https://www.uni-muenster.de/Physik.TP/research/kulesza/leptoquarks.html

Two restriction cards that define S1 and R2 models are also included.