Abstract out Server functionality into pluginland

[balupton]

v6.81 will remove all server functionality from DocPad, and place it into pluginland. A serve plugin will be introduced which merely serves the out directory with no dynamic abilities. This will dramatically simplify the codebase, improve performance, and bring DocPad into relevance once again as an excellent static site generator.

Background reading:

• Deprecation notice of dynamic abilities
• Operation Disassemble & Diversify #821
• DocPad Database Architecture Vision #705
• Shutting down DocPad? #1072

Closes:

• Plugin: Search #42
• Warn the user if they run docpad generate and have dynamic documents #301
• Reports that serverHttp and serverExpress must be inside server option to work correctly #457
• When a user creates a dynamic page, warn the user if they don't have the cleanurls plugin installed #521
• Bug: DocPad Router doesn't handle URL escaping #602
• Render documents as we need them #629
• Bug: Webserver + docpad-plugin-multiplelayouts #696
• Docpad not serving without a generate action #741
• Heroku Woes with Docpad 6.59.6 #750
• Dynamic pages after 6.57.3 #767
• General Server Roadmap #768
• Http request for file that does not exist crashes docpad #778
• 404 middleware #779
• how to insert dynamic files create #827
• Updated files not updated when viewing in browser #830
• Integrating Docpad and Express #835
• MIME types #876
• Error: Service Unavailable #1057
• DocPad should output which environment variables it used for the listening address #1058
• serverExpress is ignored unless serverHttp is also set #1060
• Migration to Express 4.x and updating dependencies: Log of progress and questions related. #1065
• Dynamic variable while rendering documents #1067
• Abstract out Server functionality into pluginland #1081