* Move some common functionality
* Move setupEnvironmentInfo into ExtensionContentController
* Move background/environment.js to extension/environment.js
* Move comment
* Add DocumentUtil.isInputElement
* Use DocumentUtil.isInputElement
* Fix simple hotkeys (shift or no modifier) preventing text field input
* Improve input detection
* Validate key is an input character before blocking hotkey
* Simplify
* Fix incorrect property