Extension:CentralNotice/Notes/Documentation rewrite


 * Extension:CentralNotice General intro for developers, installation instructions, terminology and general usage.
 * Subpages of Extension:CentralNotice Hodgepodge of notes and explanations, some current and some not.


 * Help:CentralNotice General instructions for CentralNotice administrators.
 * CentralNotice Links and summaries for several bits of CentralNotice documentation for administrators, translators and users in general.

Proposal

 * A single landing page with an overview and links to documentation for users in different roles.