* Add support for injecting stylesheets into a custom parent node
* Add api.getStylesheetContent
* Add support for injecting a CSS file's content
* Add usePopupShadowDom option
* Use a per-parentNode cache
* Add support for using a shadow DOM wrapper around popup iframes
* Ignore the popup container instead of the frame
* Convert api.js into a class instance
* Use new api.* functions
* Fix missing binds
* Group functions with progress callbacks together
* Change style
* Fix API override not working
* Remove unnecessary load of /fg/css/client.css
* Replace dynamicLoader.loadStyles with dynamicLoader.loadStyle
* Replace Popup._injectStylesheet with dynamicLoader.loadStyle
* Remove unused global
* Validate document.body before use in loadScripts
This also fixes an issue where reject wasn't being passed to loadScriptSentinel.
* Validate document nodes before use in _getSiteColor
* Validate document.body before use in _getViewport
* Validate document.body before use in setContentScale
* Validate document.body before use in docImposterCreate
