Resolve remaining MeSH Tree Numbers on native CL classes

[ghost]

Following up on the work done in #1558, this issue resolves the remaining MeSH Tree Numbers that were unmapped in native CL classes.

See Action items below:

ID	Label	Current TreeNumber	Proposed UniqueID mapping	Action
CL:0000568	amine precursor uptake and decarboxylation cell	MESH:A11.070	D001078 "APUD Cells"	Replace Tree Number with Unique ID. Move reference annotation to whole class, not defintion.
CL:0000132	corneal endothelial cell	MESH:A09.371.060.067.31	N/A- Did not find. Did find D004728 "Endothelium, Corneal", (A09.371.060.067.318), which appropriately appears as an annotation on UBERON:0001985 'corneal endothelium'.	Remove Tree Number. If a substitute is demanded, consider adding MESH:D004728, but may be redundant (already on UBERON term). Consider adding MESH:D055954 "Corneal Endothelial Cell Loss", but may not be appropriate scope (pathology) although it also references cell type.
CL:0000333	migratory neural crest cell	MESH:A16.254.600	N/A- Did not find.	Remove Tree Number. No suitable MeSH substitute identified. Replace with dbxref doi:10.1016/j.stem.2015.02.017
CL:0000577	type EC enteroendocrine cell	MESH:A03.492.766.440.250	D004759 "Enterochromaffin Cells"	Replace Tree Number with Unique ID. Move reference annotation to whole class, not defintion.
CL:0000588	odontoclast	MESH:A11.329.679	N/A- Did not find.	Remove Tree Number. No suitable substitute identified.
CL:0000547	proerythroblast	MESH:A11.118.290.350.200	N/A- Did not find. Closest appears to be D004900 "Erythrolasts" with related concept "Proerythroblasts".	Remove Tree Number. No suitable substitute identified.

Additionally, update editor doc advising to use MeSH Unique ID numbers, not Tree Numbers, in annotations.