Added proper get_nodes for a phase, distinct from get_cumulative_nodes for a phase and all ancestors
Updated tests to use get_cumulative_phase_nodes
distinguish get_cumulative_nodes from get_nodes and move back to using properly scoped DBSession in get_object_or_404 (since it'll always return the same session within a request/response
Render this phases nodes as separate layer from its ancestors (unless this is the root phase)
adding bootstrap-tab, required for the Auto/Manual tab selection