Adding LO_LQ_S1 for AGENE-1714

Requestor: Yoav Afik

Contents: S1 single leptoquark model

Paper: https://arxiv.org/abs/1801.07641

Source: https://lqnlo.hepforge.org/

JIRA: https://its.cern.ch/jira/browse/AGENE-1714