added foreign keys to seqr.model schema classes to make migration easier
added foreign keys to seqr.model schema classes to make migration easier

macarthur-lab/seqr,ssadedin/seqr,ssadedin/seqr,macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/xbrowse,macarthur-lab/seqr,macarthur-lab/xbrowse,macarthur-lab/seqr,ssadedin/seqr,macarthur-lab/seqr,macarthur-lab/xbrowse,macarthur-lab/seqr,ssadedin/seqr,ssadedin/seqr,macarthur-lab/xbrowse