Custom Fields for Page templates

This is to hide custom fields from pages when restricting fields to
page templates only. Before it would only hide the fields after you
saved the page. Now we can set it to only show after the template is
selected in the drop down.
Changed Shortcode comment

Changed short code description to reflect correct usage.
Better Excerpt Function

Removed the html5_excerpt function. Added a custom_excerpt() that
actually works as expected.