Update ManualImageCrop.php

Added generation of @2x (retina) versions of the crop
Update ManualImageCrop.php

fixed old references to $src_w2x and $src_h2x
Update ManualImageCropEditorWindow.php
Added UI for generating Retina images

added checkbox and status info on main MIC window to support retina
images
fixed checking src img width to determine if 2x is possible
add wp_option to remember make2x choice
fix movement from show/hide mic-2x-status
Minor 2x UI tweaks

CSS tweaks to fix show/hide jitter in 3.8 and fix status icon loading
too early
Merge pull request #6 from spwarner/master

Update ManualImageCrop.php