group pinned apps

[johrstrom]

Fixes #920

group pinned apps by their original category and add a heading for each section. This is essentially making the dashboard#index with pinned apps the same as apps#featured (i.e., shared apps).

It is slightly different in the way the widgets are arranged (how they interact with the MOTD and the XDMOD panels) but the partials to generate the rows in app/views/dashboard/pinned_apps are basically carbon copies of similar partials in app/views/apps/. (only these headings are h4 instead of h2)

apps#featured

dashboard#index

[johrstrom]

#920 indicates configurable branding for these headers. This PR does not include that, but it can.

[ericfranz]

So right now this groups by 100% of the time.

#920 had the idea of in the pinned_apps configuration being able to specify a single group_by: KEY where one option would be group_by: category (which would use original category) or group_by: METADATA_KEY_NAME such as group_by: field_of_science or group_by: type etc.

But if group_by: was omitted from the pinned_apps config, no grouping would occur.

[johrstrom]

OK, I'll add that.

[johrstrom]

I've added the functionality to group by known fields (category, subcategory, owner etc). Metadata fields I can have in another PR.

Note that this adds a new config pinned_apps_group_by instead of having the key inside the pinned_apps to avoid funny marshaling or having to expand the structure of pinned_apps from an array to a map. But that can easily be changed.

[johrstrom]

Note the structure of these new files in views/dashboard/pinned_apps (the pinned_apps being the new directory). I figure we're going to get a lot more views as time goes on. Just a heads up that there's a new directory.