Juvenile Justice; Permits juvenile with one prior sealing or expunction to obtain court-ordered expunction; provides court may retain post disposition jurisdiction until child reaches age 21 for certain youth on post-commitment probation; revises provisions relating to disposition hearings; provides for tolling of probation period when notice of affidavit of violation is filed until allegation is resolved; revises maximum amount of time juvenile may be committed to juvenile corrections facility; revises age ranges of juveniles who may be committed to such facilities; revises offenses that permit juveniles to be committed to such facilities.