Rename MergeLabelMapFilter enum to Pascal Casing Style

On windows STRICT is defined, and can't be used. So we change the
style used.

Change-Id: I57d512656c8f297aa76f0941dcd08436730c6eb8
Adding test for MergeLabelMapFilter's enum

Change-Id: I8103917a5bcfb27a801fb4097a795ee28880b76c
Wrapping LabelUniqueLabelMapFilter

Change-Id: I101ca896737b9f648cb00d486505cb2a5c63059d
Merge topic 'SIMPLEITK-298_AddMergeLabelMapFilter' into next

47943b8e Wrapping LabelUniqueLabelMapFilter
76713192 Adding test for MergeLabelMapFilter's enum
b1442a1f Rename MergeLabelMapFilter enum to Pascal Casing Style