Set 'skin' template parameter rather than override parent method

BaseTemplate's getSkin() method is perfectly adequate if you simply set a
skin value where it expects it. Doing so obviates the need to reimplement
getSkin() in UserloginTemplateVForm and UsercreateTemplateVForm.

Change-Id: Icd22de2218fc96cb67c11d0c1763b607743fe3b6
Merge "Set 'skin' template parameter rather than override parent method"