Capture metrics for problem attempts and histograms of problem grades
Make new-style chinese language codes works for translation

The old-style chinese language codes used in django 1.4 series are now deprecated, as discussed here:  https://code.djangoproject.com/ticket/18419.
Although majority of browsers still use the old-style language codes, some new browsers such as IE11 in Windows 8.1 start to use the new-style names instead of old-style ones which makes the current chinese translations of edX can't work properly under these browsers.
As there is no easy way for edX to change a higher version of django, I think we could do some mapping here so that the users who use IE11 in Windows 8.1 or other browsers that use the new-style names can view correct translations.
Also, this fix will make users who use one of the language codes:  zh-hk ,  zh-sg  and  zh-mo  can see the correct translations.
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
Merge pull request #3044 from edx/sylviapearce/documentation/DOC-191

Sylviapearce/documentation/doc 191
Grading Documentation Update

DOC-97
DOC-176

Added note about grading subsections only, and vertical bars
representing subsections in progress tab
Temporarily disable studio acid block tests that are failing
Merge pull request #3174 from edx/zoldak/disable-acid

Temporarily disable studio acid block tests that are failing
Merge pull request #3171 from abdoosh00/unicode-fixes

unicode fixes
Merge pull request #3137 from edx/markhoeber/documentation/doc-97

Changes for doc-97 - Subsection grading
Initial draft and images for LMS-2381