ACF PRO v5.1.0 update

Changelog

• Google Map field: Fixed JS bug causing navigation prompt to incorrectly appear
• Image field: Added width & height data next to preview_size settings
• Image field: Added width & height data next to preview_size settings
• Options page: Fixed bug where validation error would prevent submit button from working
• Core: Fixed bug where previewing a post would fail on every odd attempt
• Core: Fixed bug with persistent cache when editing field groups
• Core: Added support for widget JS functionality in the customizer
• Core: Changed stripslashes setting to false to allow values with back slashes
• Core: Minor fixes and improvements