Add "show-hide" key to show_on arg

Add the ability to set “show-hide” as key for the show_on argument.
This would take an array of page templates as the matching value pair.

The meta box would be generated for all pages. However it would be
hidden by $.hide() unless one of the declared page-templates is
selected in the “Page Attributes” Template select menu. At this point
it is displayed by $.show();

UPDATED 07/18/2014 7:15PM ET:

"Add post_radio, post_select and post_multicheck"
Created 3 field types, post_radio, post_select and post_multicheck that
offer the same options for post types as already exists for taxonomies.

UPDATED 07/20/2014 2:16AM ET:

Added ‘multiselect’, ‘post_multiselect’, ‘taxonomy_ multiselect’ and
‘chosen’ field types.

The main purposes for adding the multiple select field types were to
use them with the chosen field type.

Chosen.js converts HTML form select fields in to more user friendly
versions.

UPDATED 07/20/2014 2:26PM ET:

Added the ‘radio_image’ field type which allows an argument of an image to be set to replace the radio button and label.