Show category image preview when editing a category (if one exists).
Use HTML5 number field type for integer fields in the admin.
Use HTML5 number field type for new category thumbnail size fields.
Merge pull request #448 from benhuson/number-fields-in-admin

Use HTML5 number field type for integer fields in the admin.
Merge pull request #447 from benhuson/category-thumbnail

Show category image preview when editing a category (if one exists).
Cleaning up a bit on the new preview category image
Moving inline styles to CSS for category image preview in admin.