Fix saving image dimension file sizes.

This has been broken for YEARS. I noticed it over the file sizes were not saving over a year ago, and did a bunch of debug and traced it back to Imagick not returning a file length or size after the Imagick is cloned. I reported a bug then (https://bugs.php.net/bug.php?id=64015) which pointed the finger at upstream Imagick behaviour. This works around the fact that cloned Imagick instances cannot get filesize by saving a temporary file, loading it again with a new instance, and grabbing the filesize from that.
Use php's filesize to get the dimension binding's filesize instead of the slower imagick path.
Dimension binding filesize saving has to happen after the files are saved.

This ends up saving the binding twice. We want to save it before saving the file to disk to make sure there are no exceptions in the sql to prevent orphans, so we need to do the filesize processing after the file has been saved.
WS
use getDimensionBinding to get the binding
Merge pull request #2 from nburka/isaacgrant-save-dimension-sizes

use getDimensionBinding to get the binding
Merge pull request #79 from isaacgrant/save-dimension-sizes

Fix saving image dimension file sizes.