Begin implementing power lines

The idea is that the user will tap a building to begin the power line,
tap zero or more connecting points on the map where pylons will be
placed and finally tap another building to terminate the connection.

So far, only the basic model and 'setter' functions have been
(partially) implemented.
Change the 'Build Powerline' icon

I don't know what the license of this image is, so it should be replaced
before the game is released.
Add a custom BuildingList collection

The collection itself and its buildingAt function, which returns true if
there's a building at the given coordinates (x,y) and false otherwise,
both work.

However, there's a bug present which causes the applications BuildingList*
to always be empty. It's a valid collection, but its length is zero.
Fixing this bug has proved to be tricky.

* app.gameLevel.get("map").get("buildings") in the browser console
Add a function for translating zoomed to absolute map coordinates
Add event handling for building power lines

The graphics are still missing, but the underlying logic is there.
Unquote object keys in map.js and player.js

This is consistent with the other models, and feels more JavaScripty.
Remove loading of a non-existent image in imageLibrary.js
Add a collection to actually save created power lines
Begin implementing graphics for power lines

They're incomplete, buggy and ugly, but it's a start. Currently,
power lines are only visible in 'overview' mode.
Merge remote-tracking branch 'origin/master' into powerlines

Conflicts:
	www/js/models/map.js
	www/js/models/player.js
	www/js/views/screen.js
Map goes to zoomed view before building powerlines

.
Change drawing of powerline

Powerlines now gets drawn from the center of the building they are connected to.
Merge branch 'master' of https://github.com/kpro-gr10/Power-Supply into powerlines

Conflicts:
	www/js/views/hud.js
	www/js/views/screen.js