Refactored Video.title_display()

title_display() was pretty weird.  It would truncate the title to 35 chars by
default (although it added "..." at the end, so really 38 chars), but most
uses of the function actually didn't want the truncation.  And many pieces of
code assumed that it wasn't truncated and performed their own trunctation.

Changed it so Video.title_display() returns the full title.
Added SubtitleLanguage.title_display() and SubtitleVersion.title_display()

Removed Video.get_title_display(), which was redundant and would
return the same value as video.title_display(truncate=False).

Refactored the code to calculate titles for the video templates
(video-view.html and subtitle-view.html).  Before we had several
(fairly complicated) pieces of code to calculate the title.
Refactored things so the 1 place we calculate it in is the
videos.views module.  This reduces duplicate code, makes things
easier to test, and easier to translate.  This changes our title META
tags very slightly.
Add a way for apps to override other app's functions
Add speaker name to titles for TED videos (#758)

Added a new module called amaradotorg.  It's going to contain code
like this that's specific to our website and customizes the core
functionality.
Fixed bad method call
Fixed titles for video pages

I was a bit overeager to use the page_title variable for all title
text.
Merge branch 'staging' into gh-758

Conflicts:
	settings.py
Merge pull request #832 from pculture/gh-758

Gh 758