make embargo template theme-able

Use "Stanford-style" theming to enable you to put your own embargo
notice up.
missing themed embargo page fails safely to unthemed
updated pdf viewer
Convert CAPA inputtype statuses from strings to objects, in order to
simplify css class management and internationalization of status strings
(potentially) displayed to the user.
Add some optional policies around password resets, such as password reuse, forced password resets, allowed frequency of password resets
password history: just limit the result set range to simplify iteration logic
Fix flaky acceptance test.
Fixed studio can't handle more than 9 lines in advanced settings.
STUD-1483
Fixes LMS-1740 by activating the zooming diagram with the spacebar.
Capture metrics for problem attempts and histograms of problem grades
Fix bad interaction between pluggable InputTypes and Microsites

Pluggable InputTypes use edxmako.paths.add_lookup to inject new
mako template directories. Those were getting clobbered by microsites
(and by theming), which were completely rebuilding the mako template
lookup list from scratch.

This commit switches those two features to use the same add_lookup
function as pluggable InputTypes.

[LMS-2489]
Display transcript translations for student in their source language.
Fix acceptance tests.
Wait for big subtitles to render.
Set big timeout for big subtitles.
unicode fixes
line fix
Merge pull request #3162 from cpennington/problem-check-metrics

Capture metrics for problem attempts and histograms of problem grades
Merge pull request #3148 from louyihua/localization-fix

Make new-style chinese language codes works for translation
Instructor- and student-facing documentation for ORA2