Minor updates to stay up with ctools; remove deprecated panel_node_viwe task handler, as it will now always be panel_context

Some major restructuring, catching up to CTools. This is very much in process, there is a huge list of things that need to happen here still, but this may be checkpoint usable to the strong-stomached.

More tweaks to panel delegator stuff, including moving more work from the plugin to delegator.inc and displaying information about the panel display in a delegator dropdown.

Changed post-arg context build check to be aware of the fact that we now use error codes for argument plugins, and it should only load add'l contextual data if the return is an object (aka, isn't numeric)

Updated panels_load_include() to prevent the re-inclusion of already-loaded include files. Hackish, but eh.

Major cleanup, moved several more functions out to include files, removed some crufty ones. Also refactored the master loader itself some more.

Got rid of a leftover use of $panel_page->pid, and updated the alternate admin menu structure to the current approach.

Moved panels_page_access() and panels_page_get_title() into the read inc; also made temporary modifications to the former that (hackishly) cope with the pre-emptive access checking on all links.

Stupid (evidently) unncessary call to panels_context_load_contexts() seems to have been the whole problem. Contexts are now being loaded properly...YAAAAAAAR!!!!!!!

This means we may well be ready for the first alpha release...

Some refactoring, partially to accommodate changes suggested by douggreen. The basic context-loading problem has not yet been solved, however.

by douggreen: re-added missing callback property to the validate function. Might actually not be necessary...we'll see.

by douggreen: Removed additional t() calls; added str_replace() to exporter to match coding standards.