Re-define `Post_Metabox` using conventional WordPress code

[brylie]

Problem

The Post_Metabox is currently defined using the Queulat package.

creativecommons-base/inc/metaboxes.php

Line 8 in 39e7252

class Post_Metabox extends Metabox {

Since we have established a consensus to deprecate the Queulat package, we need to re-create the Post_Metabox using conventional WordPress code.

Task

• Determine what fields are needed for the Post_Metabox
• Determine how the metadata should be processed and stored
• Re-create the Post_Metabox using conventional WordPress code
• determine whether a more class-name meaningful name would be useful (if applicable)

[nox1134]

Hi @brylie ! I'd like to work on this issue.