Edit Image modal:
- Move all advanced options under a single “Show advanced options” toggle that mirrors the behavior and look-and-feel of the wplink modal.
- Switch to using <select> for the Size and Link To.
- Bring back the field for CSS Class for the image, but don’t incorporate the internally managed WordPress classes (size-, wp-image-, etc…).
- On larger screen sizes, float labels to the left. When the width drops below 900px, stack the label above the fields.
- Keep image at top on screen sizes where the two columns are stacked into a single column.
- Don't replace the nodes in the editor DOM so we don't stomp on any custom attributes that the user may have added via the Text editor or some other mechanism.
Props gcorne, see #27366

git-svn-id: https://develop.svn.wordpress.org/trunk@27898 602fd350-edb4-49c9-b593-d223f7449a82