Fix menu postion parameter again

Tries to do what this one couldn't.

Fixes Placeholder error and reformats tag output for Datetime fields

Some select fields' placeholder retrieval was not protected causing an error. Datetime fields saved under a taxonomy are now output in a more human readable way.

Time/Datetime term description now contains timezone

A named timezone is now stored in the description of the taxonomy term that the datetime/time field is saved as. This is used for ICS file generation and timestamps, as it is difficult to get a named timezones from time-deltas.

Date/Time/Datetime fields now can be repeated

Before this release, date/time/datetime fields could not be repeated because each requires a unique taxonomy. This allows for the repetition of these fields. However, usage should be handled with caution. The date field still needs to have a taxonomy associated with it, but it saves no terms under it. The date data is saved in the posts metadata only. Additionally, regular standalone date fields(that aren't repeated) still work the same way as before.

This isn't the best solution, but it's the easiest to implement given the timeframe and backwards compatibility.

Custom File Upload field creates attachment

When uploading a file through the custom file upload field, the file's data would be stored exclusively in the meta-data which isn't optimal. This creates an attachment for each file uploaded, conforming to the WP workflow.

Fix saving bug that prevents fields after an empty link field from saving

A link field is set to null when no value is given, which caused the save function to return early. That early return caused the subsequent fields to not save.

Fix menu postion parameter

When registering a post type, the menu position argument must be an integer so the current argument had to be changed.

Adds checkbox to toggle Featured Image

Featured Images that appear on blog posts are now able to be turned on/off at the discretion of the content editor if/when the featured image thumbnail is shown in the blog post feed to avoid repetition.

Set menu names for custom post types to be plural

Changed

• Names of our custom post types in the sidebar to be plural, matching the
  standard for default WordPress post types.

Change field type for URLs to allow entering relative URLs

Changed

• url field output (in the meta box) from tpe="url" to type="text",
  so that relative URLs will not fail native browser validation.