pyClothingItem index safety and extra properties

[Jrius]

pyClothingItem was missing a few things to be properly usable, so I made the following modifications:

• Added constants pyClothingItem.kNumLODLevels and pyClothingItem.kLayerMax.
• Added pyClothingItem.numElements getter (as well as matching plClothingItem::getNumElements()).
• The following will throw an IndexError when appropriate instead of crashing:
  • getElementTexture
  • setElementTexture
  • getElementName
  • setElementName
  • delElement