MolFromMolBlock should correctly assign stereochemistry to 3D molecules

[greglandrum]

Describe the bug
Here's a demo:

In [15]: print(mb)

     RDKit          3D

  0  0  0  0  0  0  0  0  0  0999 V3000
M  V30 BEGIN CTAB
M  V30 COUNTS 5 4 0 0 0
M  V30 BEGIN ATOM
M  V30 1 C 0.900794 -0.086835 0.009340 0
M  V30 2 C -0.552652 0.319534 0.077502 0
M  V30 3 F -0.861497 0.413307 1.437370 0
M  V30 4 Cl -0.784572 1.925710 -0.672698 0
M  V30 5 O -1.402227 -0.583223 -0.509512 0
M  V30 END ATOM
M  V30 BEGIN BOND
M  V30 1 1 1 2
M  V30 2 1 2 3
M  V30 3 1 2 4
M  V30 4 1 2 5
M  V30 END BOND
M  V30 END CTAB
M  END

In [16]: nm = Chem.MolFromMolBlock(mb)

In [17]: nm.Debug()
Atoms:
	0 6 C chg: 0  deg: 1 exp: 1 imp: 3 hyb: 4 arom?: 0 chi: 0
	1 6 C chg: 0  deg: 4 exp: 4 imp: 0 hyb: 4 arom?: 0 chi: 0
	2 9 F chg: 0  deg: 1 exp: 1 imp: 0 hyb: 4 arom?: 0 chi: 0
	3 17 Cl chg: 0  deg: 1 exp: 1 imp: 0 hyb: 4 arom?: 0 chi: 0
	4 8 O chg: 0  deg: 1 exp: 1 imp: 1 hyb: 4 arom?: 0 chi: 0
Bonds:
	0 0->1 order: 1 conj?: 0 aromatic?: 0
	1 1->2 order: 1 conj?: 0 aromatic?: 0
	2 1->3 order: 1 conj?: 0 aromatic?: 0
	3 1->4 order: 1 conj?: 0 aromatic?: 0

if we call AssignStereochemistryFrom3D() then the chiral center is recognized:

In [18]: Chem.AssignStereochemistryFrom3D(nm)

In [19]: nm.Debug()
Atoms:
	0 6 C chg: 0  deg: 1 exp: 1 imp: 3 hyb: 4 arom?: 0 chi: 0
	1 6 C chg: 0  deg: 4 exp: 4 imp: 0 hyb: 4 arom?: 0 chi: 1
	2 9 F chg: 0  deg: 1 exp: 1 imp: 0 hyb: 4 arom?: 0 chi: 0
	3 17 Cl chg: 0  deg: 1 exp: 1 imp: 0 hyb: 4 arom?: 0 chi: 0
	4 8 O chg: 0  deg: 1 exp: 1 imp: 1 hyb: 4 arom?: 0 chi: 0
Bonds:
	0 0->1 order: 1 conj?: 0 aromatic?: 0
	1 1->2 order: 1 conj?: 0 aromatic?: 0
	2 1->3 order: 1 conj?: 0 aromatic?: 0
	3 1->4 order: 1 conj?: 0 aromatic?: 0

There is logic in the mol block parser to assign stereochemistry to 3D conformers: https://github.com/rdkit/rdkit/blob/master/Code/GraphMol/FileParsers/MolFileParser.cpp#L3153
but this ends up not being called if there are no wedged bonds. That doesn't make sense... we shouldn't require wedged bonds in the case of a 3D conformer.

Configuration (please complete the following information):

• RDKit version: all
• OS: all