Infrastructure to display configured template in overview

It might be desirable to have different layouts on the overview, so a
simple way of achieving this is to make it possible to configure which
template (must exist) to use in the admin section.
Add `Task` collection

Main collection which will hold the jobs that are currently ongoing etc.
Add simple way of bootstrapping data

Make it easy to get test data into the system. This will save time in
the future. Right now, just enter the corresponding collection data in
the `private/bootstrap/data.json` file and they will be inserted into
the database if there are no collections there already.

If a new collection, also add a mapping from collection name to
collection instance in `collectionNameToCollection` (there's no way in
Meteor to do this that isn't super ugly).
Add better bootstrap data
Add stylus package
Add mockup items to default overview template

Fetch all tasks from the database and att them to the router data
context.

Add some rudimentary displaying of tasks in a tile-like structure
without much design to it yet.
Merge branch 'overview-mockup'
Add note about demo site