MA-157 Mobile analytics end-to-end.
Move app-generated context back into properties.
Ignore BI events through segment's webhook.
Ignore events without Data in Properties.
Corrected Import Statement
Merge pull request #6172 from edx/mobile/update-analytics

MA-157 Move context back into properties.
Fix import statement.
Merge pull request #6208 from edx/clintonb/release-fix

Corrected Import Statement
Move images from common to LMS that are only used in LMS

OPEN-328
Remove image that is duplicated in LMS and CMS

OPEN-328
Remove duplicate image files

spinner.gif and spinner-on-grey.gif are the same file.
Explicitly give the LMS a spinner.gif file.

OPEN-328
Move wiki icons to the LMS, where they are used

OPEN-328
Rename pl-faculty.png to placeholder-faculty.png

OPEN-328
Replace 'mit_dome.jpg' and 'simple_graph.png' with a default placeholder image