Removed obsolete Extensions project.
Updated the projects to .NET 4.5, MVC 4 and Web Pages 2.0
Converted old Url.Content to the new MVC 4 syntax. Added the ToolbarItem class.
Totally rewrote the extension management with Microsoft MEF.
Added so extensions from App_Code i loaded.
Changed MEF import to Property to avoid compilation warnings.
Removed old method from Piranha.Config
Using WebPiranha.GetSiteUrl() for site links in manager

Fixes port not being included in top-left site link's href and
permalinks on Edit pages; also updated Preview links to use GetSiteUrl()
for consistency
Fixed issue with dates in sitemap wrapping onto multiple lines causing the sitemap layout to fail
First commit for the restructuring with MVC 4 support
Removed razor generator file that happened to be included in the mvc template.
Added UI.Controller() for Piranha.Mvc
Updated the web.config.transform and added default area web.config to the TemplateSite.
Made the application self registered to reduce modifications needed to include the framework.
Updated TinyMCE editor to 4.0.1b. Added media dialog, see issue #80.
Fixed floating toolbar for TinyMCE 4.0
Fixed missing "up one folder" icon in the media-dialog.
Fixed so that the permalink handler doesn't "steal" the request in no handler is installed.

If Piranha.Mvc or Piranha.WebPages isn't installed request should be
handled by the regular application.
Fixed PostRegion in Entities.PageModel. By @Urreman
Fixed so that posts can be accessed when surfing a site outside of the default namespace.