promotecontroller: Fix long lines

Remove unused 'subk' variable
Promote_Graph: Move logic out of template
Promote_Graph: Add predicted impressions

The admin view of Promote_Graph will now show the
predicted impressions. This also stubs out the
scheduled impressions.
promote_graph.html: Add 'scope="row"'
promote_graph: Use CSS to capitalize headers
Move _cost_per_{mille,click} functions to promote.py
Use promote.cost_per_X functions in Promote_Graph