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
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
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.
Revert "Open ended panel headings not internationalized."

This reverts commit eb9133aeb687c0d103feec16371ad7d2bce952a8.

ORA-352
Merge pull request #3168 from cpennington/fix-lms-2489

Fix bad interaction between pluggable InputTypes and Microsites
Fixes potential 'too many open files error' when running all servers.
Merge pull request #3176 from edx/hotfix/revert-openended-i18n

Revert "Open ended panel headings not internationalized."
Check iframe src for the specific value TinyMCE uses.

STUD-1470
Add synchronization for rendering to studio xblock tests
remove double icons in the wiki sidebar
Add repsonse pagination to inline discussions