added 4 heteropolycyclic thermo groups

4 new thermo groups are added for heteropolycyclics containing one or two
oxygens. These thermo corrections are calculated using the CBS-QB3 method.
s3_5_6_ane_hetero_O and s3_5_6_ane_hetero_OO are added as children of
s3_5_6_ane.
s4_6_6_ane_hetero_O and s4_6_6_ane_hetero_OO are added as children of
s4_6_6_ane.