added some remote data test sources
flushed out abstract interface for data provider
constructing default data provider in start.py
implemented data source listing capability
started remote data source

Conflicts:
	bokeh/serverconfig.py
changed remote data test to use our server config/client object
list_data_sources on hdf5 backend shouldn't try to get current_user, that gets passed in already
support for line downsampling on the server
- redid sample data to use table format
- moved manual downsample example to server from cloud, using new line_downsample function
- redid line_downsample function with better function signature
error handling for when we should not do downsampling
line downsampling working
release files
fixing server urls
throttling
heatmap downsampling
wip