closes#6534
- new input fields in general settings incl. validation
- facebook and twitter as new models in settings.js
- adds values for facebook and twitter to default-settings.js
- adds blog helpers for facebook and twittter
- rather than saving the whole URL, the Twitter username incl. '@' will be extracted from URL and saved in the settings. The User will still input the full URL. After saving the blog setting, the stored Twitter username will be parsed again as the full URL and available in the input field. A custom transform is used for this.
- adding meta fields to be rendered in {{ghost_head}}:
- '<meta property="article:publisher" content="https://www.facebook.com/page" />' and
- '<meta name="twitter:site" content="@user"/>'
- adds facebook and twitter to unit test for structured data
- adds unit test for general settings
- adds acceptance test for new input fields in general settings
- adds a custom transform for twitter model to save only the username to the server
- adds unit test for transform
no issue
- adds `gh-image-uploader` that handles image uploads in a fully ember fashion and with no dependency on `uploader.js`
- adds `gh-image-uploader-with-preview` that can fully replace the old `gh-uploader`
- replace uses of `gh-uploader` in PSM & TSM with `gh-image-uploader-with-preview`
- updates the editor preview image handling to use the new `gh-image-uploader-with-preview` component
- updates the image upload modal to use `gh-image-uploader` (utilises the `saveButton=false` flag which means the preview has to be handled externally to avoid auto-replacement when typing a URL)
- removes all old `uploader.js` related code
- adds custom `RequestEntityTooLargeError` and `UnsupportedMediaTypeError` errors to our `ajax` service
