Material slot names are lost when merging SkeletalMeshes

When we use the FSkeletalMeshMerge utility, material slot names are lost on the resulting mesh. We should at least transfer the first slot name found for a given material.

See UDN for more details.

We don't have a good way to test this without a debugger or doing some Blueprint changes.
So here is an easy way to test this in Bluerint:

1. In EngineTest, open the SkelMeshMergeActor blueprint and add the following log nodes to the end of the graph. Compile.
   [Image Removed]
2. Open the SkelMeshMergeMap and launch it in PIE

Result: The "Output Log" window is filled with "VisLogBP: LogText: 'None'" showing that no slot name is present on the merged mesh.
Expected: The "Output Log" window shows:
VisLogBP: LogText: 'M_UE4Man_Body'
VisLogBP: LogText: 'None'
VisLogBP: LogText: 'M_UE4Man_Body'
VisLogBP: LogText: 'None'
VisLogBP: LogText: 'One'
VisLogBP: LogText: 'Two'
VisLogBP: LogText: 'M_UE4Man_Body'
VisLogBP: LogText: 'None'
VisLogBP: LogText: 'One'
VisLogBP: LogText: 'Two'
VisLogBP: LogText: 'M_UE4Man_Body'
VisLogBP: LogText: 'None'
VisLogBP: LogText: 'One'
VisLogBP: LogText: 'None'
VisLogBP: LogText: 'Two'
VisLogBP: LogText: 'One'
VisLogBP: LogText: 'None'
VisLogBP: LogText: 'Two'
Indicating that the SlotNames were not lost during the merge (slot names at 'None' were already set to 'None' before the merge).

Build freezes at "0:00:00 Gathering scene geometry... (100%)"