add image proxy service

Add a HTTP image proxy service
Use the new service for Thumbs and Artwork links
use a background loader thread for data

use a simple background loader thread
always use cached data and have the loader thread refresh the data on
each load
this is a very simple approach to using async data loading
change order loading and caching is done in

just need to load the data before the background load occures
Merge pull request #44 from faush01/master

add image proxy service