first part of #3105

Fixed

• Passing props through to react templates rather than model, view
• classes function in reactHelpers.js now removes duplicates
• img[loading=eager] fix now uses React.createElement rather than template modifications (which didn't work with class based react components)
• various eslint issues specific to react
• fixed header.jsx so that it outputs correctly if no value is specified

Changed

• parials/component.jsx has become header.jsx as it can be used for articles, blocks and pages later
• Renamed AdaptView.isReact to AdaptView.isJSX as it's more precise

Removed

• reactHelpers.js clone, find and render functions as unnecessary

Added

• image.jsx to centralise and perform automatic graphic switching throughout jsx templates
• reactHelpers.js prefixClasses function, to aid template class creation where component and accordion are prepended to __inner and __widget
• exposed isInteractive from questionView.js for use in jsx templates