Issue #1268902 by John Morahan: Panelizer task handler did not properly test to see if the node is actually panelized, inadvertently short circuiting other variants.

Issue #1175556: Reverting reset feature because it was written without enough understanding of how the form is used.

Since this module depends on page manager to render the panels display
of panelized nodes, we check if the 'node_view' page template is disabled.
If so, we warn site admins to help them configure this properly.

This moves a bunch of logic for rendering the panelizer panels display
for a given node out of plugins/task_handlers/panelizer_node.inc into
a new shared helper function, panelizer_render_node() so it can be
reused by panelizer_plugin_row_panelizer_node_view::render(). The row
style is a child of views_plugin_row_node_view, and adds an option for
how to handle non-panelized nodes (let the parent render them as normal
nodes with settings for build mode etc vs. hide non-panelized nodes).

- Added hook_node_delete() to clean up when nodes are deleted.
- Added the ability to reset a node to its default panel.