More objects -> models renames
Remove bokeh.{objects,glyphs,widgets} modules
Fix import of bokeh.models.glyphs in bokeh.plotting_helpers
Fix imports in bokeh.server.start
Rename objects -> models in _preload_models()
Rename bokeh.crossfilter.{objects->models}
Merge pull request #1505 from bokeh/mattpap/rename2

More objects -> models renames