Normalize usage of CharacterImageAvatar & UserImageAvatar Props

[mikelax]

Overview

These two components are very similar in usage, both displaying images (either of user or character) in similar display formats. The prop types around the size property is not consistent and should be normalized.

Requirements

• One component uses a string, the other a number. Sometimes it seems like the usage should be a "Semantic UI" size, other times it seems like the component needs an actual number.
• These should be normalized so the prop type and usage is the same.
• If possible, add a defaultProp to each component for this prop
• Add single line comments for these props to describe what is expected.