Fix pager links when inside .tab-pane

When loading channel playlists everything works fine - until you
click the pager links. These are picked up by the global page handler
and so replace the .main-content-panel entirely. This ignores tabbed
pagers in the global handler and adds a new one with specific handling.
Ajaxify channel videos with added pagination for good measure
Possible fix for a weird issue

For some reason when changing page on channel videos, it would
sometimes return a Google_IO error about SSL token something-or-
other. Haven't seen it since, so maybe adding a retry loop helped.

Still need to add the error view mind...
Convert to native Bootstrap tab handling

This removes the need for listening on click events and manually
showing the tab via Javascript. Instead we use the shown.bs.tab
event, and in porting to that I've reduced the code significantly.
Filter it down a bit more, cut out some variables
Fix tabs not automatically loading. Woohoo!