[12gevmoller_sim] [EXTERNAL] [JeffersonLab/remoll] 248474: add gem detector

[cipriangal]

  Branch: refs/heads/test-hevac-addTgtColl1Shlding
  Home:   https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_JeffersonLab_remoll&d=DwICaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=-0uahHXTLsQsllHBZNHgOynLaY6DUxqehsUJ91-BlNY&m=ST_6L9ieFCeWASU9BRJlXDncRL9ZUhnisQRjyrsjLwY&s=kwcmSkl3x9575pJJD9ZwMvrNQlmAtOr6-y0A04Ca4Tw&e= 
  Commit: 2484748654e0aa2850e68f9bbd2c815a952d9a6e
      https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_JeffersonLab_remoll_commit_2484748654e0aa2850e68f9bbd2c815a952d9a6e&d=DwICaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=-0uahHXTLsQsllHBZNHgOynLaY6DUxqehsUJ91-BlNY&m=ST_6L9ieFCeWASU9BRJlXDncRL9ZUhnisQRjyrsjLwY&s=DcK89h_hItsISPzvTD2ou3r-eKPPGqXfql8R5XhSQQc&e= 
  Author: Ciprian Gal <ciprian at jlab.org>
  Date:   2020-04-01 (Wed, 01 Apr 2020)

  Changed paths:
    M geometry/mollerParallel.gdml
    M geometry/positions.xml

  Log Message:
  -----------
  add gem detector