imageeditor instead of imageditor

As stated here: https://github.com/concrete5/concrete5/blob/85947736bb68730a3ca7c5f4f6124c51890e1894/build/Gruntfile.js#L150 we should have `ccm.imageeditor.js` instead of `ccm.imageditor.js`.

BTW, I see all those image_editor vs imageeditor quite confusing. Why not always using the same name? What about adopting the standard c5 convention (`image_editor`)?