Created new scaffold for the new charmstore v4 api. New app instances create a new instance of the api and pass it down the stack.
Created the getIconPath method for the v4 api and converted the handlebars helper in the charmbrowser to use the new api call
Added charmstore api v4 test suite and the first set of tests for the getIconPath method
Added app tests for the new charmstore creation
Convert the remaining calls to iconpath to getIconPath
Removed util methods which relied on iconpath and updated cascading methods
Removed old iconpath method from the charmworld v3 api and updated all remaining tests to use the new getIconPath method
Move getLocalCharmFileUrl access into the charmstore get icon path
Changed charmstore-apiv4 to just charmstore-api as per review
Created util method for fetching charm icons which dispatches to either the charmstore or the env depending on what kind of icon is required
Converted the toBoundingBoxes method to use the new utils wrapper for the getIconPath method
Merge pull request #662 from hatched/charmworld-apiv4

Create the scaffold for the new charmstore v4 api

This branch creates the scaffold for the new charmstore v4 api and injects it into the app. It also adds the `getIconPath` method and swaps the v3 version for it. At the time of writing the current jujucharms backend has issues with returning some of the icons so this branch cannot land until those fixes are made.