Adds wiki to each Site. The wiki index is accessible through SITE-BASE-URL/wiki, each page is SITE-BASE-URL/wiki/PAGENAME -same as the regular project wikis.

The wiki is a simple Grit object, not a full-on Repository model object (which would break a lot of assumptions about repos always having parent projects etc)

The repo is created the first time it's accessed for a given Site. This happens synchronously for now, as it's a one time operation per Site (do we have other reasons than perf/scaling for the usual asynch repo creation?)

Didn't end up creating any db-persisted wiki reference in the Site model: The wikis repo name/path is simply derived from Site title, e.g. 'SITENAME-site-wiki' (I assumed that each Site coexisting on a Gitorious installation has a unique name, here.)

Adds separate views for Site-wide wikis. Started looking into reusing/DRYing views and controllers between Site wiki pages and regular Pages, but seemed too fiddly - there's lots of little differences in the paths created etc so it seemed shared partials would be very small/many/parameterized?

Backend git clone/push/pull of the site wiki repos also handled and tested.

DRYed up the wiki "wikization" code into its own module in lib.

Note: discovered that wiki page->edit->preview is broken in mainline (after jQuery upgrade or something?). Will look into it and create separate merge request once I figure out how our js asset pipeline works. :)