Add lone pair denomination for R!Hx3 group in statmech to make groups R!Hx2 and R!Hx3 non-identical.

RMG-Py was detecting R!Hx1 and R1Hx3 to be equal:

R!Hx1
1 * R!H 1

R!Hx3
1 * R!H 3D

This was because 3D actually implies a single unpaired electron and 1 lone pair.
However, when the group does not have a lone pair denomination, it allows any
number of lone pairs, therefore making these two groups identical.

This is a mostly temporary fix.  These two groups are clearly overlapping when
R!Hx1 can allow any number of lone pairs including 1 lone pair.
Remove cis thermo groups that cannot be found by RMG.

Cis groups with double-labeled atoms cannot ever be incorporated into RMG's thermo
since there is no cis or trans distinction.  It makes more sense to delete them
unless we have that functionality (based on Bill's recommendation) and also
to make the database unit tests work for these.