Visit Details: removed Meter O/S for visits without DEX

• The equation for calculating Meter O/S is: 
  meter_os = ((counted_bills + counted_coins) + cashelss_from_dex) - vended_cash_from_dex 

• • Visits without DEX were displaying Meter O/S incorrectly in the absence of a DEX file, so we removed the data field and improved Visit Detail editing 
    ([expected product count - actual product count]) x price at the POS