Atom query properties

Adding query properties to structures.

Name	Description
.H+	Increase number of total hydrogens (total number of hydrogen substituents)
.H-	Decrease number of total hydrogens (total number of hydrogen substituents)
.v+	Increase number of valence (total bond order)
.v-	Decrease number of valence (total bond order)
.X+	Increase number of connections (number of substituents including hydrogens)
.X-	Decrease number of connections (number of substituents including hydrogens)
.R-	Increase number of rings (number of rings the atom is a member of)
.R+	Decrease number of rings (number of rings the atom is a member of)
.r+	Increase smallest ring size (size of the smallest ring the atom is a member of)
.r-	Decrease smallest ring size (size of the smallest ring the atom is a member of)
.rb+	Increase ring bond count (number of ring bonds next to the atom)
.rb-	Decrease ring bond count (number of ring bonds next to the atom)
.s+	Increase substitution count (number of non-hydrogen and isotopic hydrogen substituents)
.s-	Decrease substitution count (number of non-hydrogen and isotopic hydrogen substituents)
.h+	Increase number of implicit hydrogens (number of implicit hydrogen substituents)
.h-	Decrease number of implicit hydrogens (number of implicit hydrogen substituents)
.D+	Increase degree (equivalent to substitution count: number of non-hydrogen and isotopic hydrogen substituents)
.D-	Decrease degree (equivalent to substitution count: number of non-hydrogen and isotopic hydrogen substituents)
.u	Mark as unsaturated atom (atom has double, triple or aromatic bond)
.a/A	Mark as aromatic/aliphatic (has aromatic bond)