Update /builds to group projects and show last release.

This makes a few specific changes:

* Remove Project based filtering.
* Group files listed by project.
* Show last release / future release description details for each channel.

Screenshots:

Tagged Releases:
![/tagged](https://monosnap.com/image/9OqaWwRLAtxruZgayK3C82l3J.png)

Release Channel:
![/release](https://www.monosnap.com/image/pFSXV2cGbnelLcQcjIF1VGdpe.png)

Beta Channel:
![/beta](https://www.monosnap.com/image/8GyQDXm5AHo5ICBP05XWu0ebl.png)

Canary Channel:
![/canary](https://www.monosnap.com/image/FwhvFnAW4KPZDNBCstPS9HJfe.png)

@twokul - Thanks for pairing up on this!