add //label op and support \ref in latexbuilder
add //label op and support \ref in latexbuilder

suzuki/review,kuad9/review_study,masawada/review,murashitas/review,masawada/review,orangain/review,takahashim/review,takahashim/review,orangain/review,kmuto/review,suzuki/review,krororo/review,kmuto/review,murashitas/review,krororo/review,kuad9/review_study,krororo/review,kmuto/review,kdmsnr/review