Enable a configurable copyright that uses CreativeCommons

[dencold]

Right now copyright is a very simply defined via the Site.Copyright param and is visible if the Site.Params.hideCopyright param is set to false.

Let's make this simpler and add some features:

• switch copyright detail into its own top-level section
• have a standard param to handle vanilla copyright
• have a way to configure a more descriptive license from creative commons
• make sure that either configuration looks pretty on the site
• make a single easy flag to enable/disable in Site.Params
• maybe think about having copyright be configurable to specific page/tag/or whole site.