New TF-TG resources in BioGateway

We have replaced the TF-TG resources previously available in BioGateway (TRRUST, ExTRI, CytReg, Signor, GEREDB, HTRIdb, and TFactS) with the CollecTRI resource (DOI: 10.1093/nar/gkad841) and TFLink (DOI: 10.1093/database/baac083).