XElement should warn authors when shadowing asymmetric inherited attributes.

[theengineear]

While many attributes have a simple relationship to properties (e.g., .title >> "title"), there isn't a clear standard for naming conventions when it comes to properties reflecting to attributes. Some interesting cases:

class <<>> .className
contenteditable <<>> .contentEditable
aria-valuemin <<>> .ariaValueMin
itemscope <<>> ???

XElement should attempt to WARN authors when they're inadvertently shadowing attribute interfaces based on mappings between attributes and property names.

• Here's a list of global attributes (for reference) https://html.spec.whatwg.org/multipage/dom.html#global-attributes
• We should also consider all aria-* attributes as special cases.