Issue/1451 media thumbnail width

I audited all of the places we were adding media to the editor and made sure that they were being resized properly.

Media can be added from:
* Sharing content from other apps to a new post
* Selecting image/videos from a gallery app
* Capturing new photos/videos
* Adding from WP Media Library

All of those methods for adding media will now eventually get passed through ImageHelper.getScaledBitmapAtLongestSide(), which will ensure it is the correct size.

Fixes #1451 and #1407