New plugin: Import Keys

This is a new plugin that imports portal keys from a player's inventory using the Ingress app's RPC API. It loads some JSON data in an iframe and injects a script into the iframe via Firefox/Chrome or by intercepting the resource load on Android. The script in the iframe then makes an XMLHttpRequest to POST to the getInventory RPC endpoint, parses the results, and hands the results back to the main page using postMessage. The inventory results are used to update the internal state, the stored key list, and the map/UI.