Improved acf_update_field function to allow for null in condition logic rules

Signed-off-by: Elliot Condon <e@elliotcondon.com>
Fixed potential PHP error when a sub field value is not posted

Signed-off-by: Elliot Condon <e@elliotcondon.com>
Added new logic to remove meta items from the WP custom fields postbox

https://github.com/AdvancedCustomFields/acf5-beta/issues/113
Signed-off-by: Elliot Condon <e@elliotcondon.com>
Merge branch 'master' of https://github.com/AdvancedCustomFields/acf5-beta