Fixed an error in symmath_check

the expected result = 0.  symmath_check() was dividing
a quantity by the expected result, leading to a NaN value
that caused the answer to be marked incorrect.

Added test_symmath_check.py with basic tests for
the symmath_check() function.

Somehow the saves changed to just sets w/ don't send data to the server.

Feature/victor/revert revert of forums ui

Fixed a bug in symmath_check():

add a 'missing slash' regular expression for Location patterns in order ...

evaluated bool(ans), which is False when ans=0.
This led to an error message "[symmath_check] failed to get MathML for
input; dynamath=[None]" when the function reached a later condition.
The check that evaluated  bool(ans) was redundant, so I removed it.

add a 'missing slash' regular expression for Location patterns in order to account for dropped slash with the i4x:// pattern. Certain redirect cases will cause this 2nd slash to be dropped (I think via Nginx)

Feature/victor/dynamic cohorts

Have to return false from event handlers to avoid href="#"
links from sending the user to the top of the page.

See changes in xml-format.md or wiki (dynamic cohorts v1) for spec.

Add showanswer="finished" option and tests

Feature/vik/oe messages

Feature/brian/pdf js

remove empty attempts and weights from simple test course

Fix/cdodge/serializing ints as empty strings

Add more click tracking and logging to the open ended grading interface

Change test modulestore naming differentiation scheme to uuid

template name got changed. Need to reflect that on test.

Make sure temp directories are properly cleaned up so running tests does...

Feature/cdodge/metadata inheritence crawling