Add support S-group hierarchy during rendering Data SGroup information.

[IuriiPuzanov]

Example of MOL file with Data SGroups and PARENT key:

SRU1
  ACCLDraw03131513562D

  0  0  0     0  0            999 V3000
M  V30 BEGIN CTAB
M  V30 COUNTS 14 15 3 0 0
M  V30 BEGIN ATOM
M  V30 1 C 12.2108 -4.4993 0 0 
M  V30 2 C 12.4501 -3.6062 0 0 
M  V30 3 C 11.5719 -3.3709 0 0 
M  V30 4 C 11.3326 -4.264 0 0 CFG=3 
M  V30 5 C 10.5453 -4.7185 0 0 
M  V30 6 C 9.758 -4.264 0 0 
M  V30 7 O 8.9708 -4.7185 0 0 
M  V30 8 C 8.1835 -4.264 0 0 
M  V30 9 C 5.8236 -5.6323 0 0 
M  V30 10 C 6.6134 -6.0822 0 0 
M  V30 11 C 7.3962 -5.6282 0 0 
M  V30 12 C 7.3962 -4.7185 0 0 
M  V30 13 C 6.6114 -4.2644 0 0 
M  V30 14 C 5.8236 -4.7189 0 0 
M  V30 END ATOM
M  V30 BEGIN BOND
M  V30 1 1 1 4 
M  V30 2 1 2 1 
M  V30 3 1 2 3 
M  V30 4 1 3 4 
M  V30 5 1 5 4 
M  V30 6 1 6 5 
M  V30 7 1 7 6 
M  V30 8 1 8 7 
M  V30 9 1 12 8 
M  V30 10 1 14 9 
M  V30 11 2 9 10 
M  V30 12 1 10 11 
M  V30 13 2 11 12 
M  V30 14 1 12 13 
M  V30 15 2 13 14 
M  V30 END BOND
M  V30 BEGIN SGROUP
M  V30 1 SRU 1 ATOMS=(3 7 5 6) XBONDS=(2 8 5) BRKXYZ=(9 8.57 -4.94 0 8.57 -
M  V30 -4.03 0 0 0 0) BRKXYZ=(9 10.94 -4.03 0 10.94 -4.94 0 0 0 0) -
M  V30 CONNECT=HT LABEL=n 
M  V30 2 DAT 2 PARENT=1 FIELDNAME=MOLWT_DISTRIBUTION -
M  V30 FIELDDISP="   -2.4375    1.6250    DR    ALL  1    D  5" -
M  V30 FIELDDATA=1.05 
M  V30 3 DAT 3 PARENT=1 FIELDNAME=MOLWT_NUMBER_AVERAGE -
M  V30 FIELDDISP="    0.3438    1.7188    DR    ALL  1    A  5" -
M  V30 FIELDDATA=5000 
M  V30 END SGROUP
M  V30 END CTAB
M  END