Improve display of multiword product attributes

Instead of displaying a variation's custom product attributes like this: `attribute-name: attribute-value`. Display it like this: `Attribute Name: Attribute Value`.

This affects only custom product attributes set on the product, not those set in WooCommerce.

For example, the "Custom Attribute" on this product: https://cloudup.com/cxWabMgdNQ8 is currently displayed like this https://cloudup.com/cAZd6zB7TMA

With this pull request, it is displayed like this: https://cloudup.com/cVKtI6nhFTc

There will likely be unintended consequences in blindly replacing dashes with spaces and uppercasing all words, but I couldn't see a way to neatly match a variation's custom attributes against the original  names/value strings set on the variable product's attributes.