Add info about template for Checkbox problem type

Change text to "click Checkboxes on the Common Problem Types tab" and
add image of checkbox button
Correct minor formatting error
Add JSInput template information

Update Advanced Problems page with Custom JavaScript Display and
Grading (JS Input) problem info. Delete separate page for JS Input
problems. Update Appendix F with new code for sample JS Input problem.
Update JS Input to reflect new template in Studio

Update Advanced Problems file and Appendix F
Modify server_track to handle being called without a request.
Add pagination to Studio's Files and Uploads page

These changes implement STUD-813. The commit consists of the
following logical changes:
 - a REST API has been implemented for a course's assets
 - the page itself now fetches the assets client-side
 - the Backbone.Paginator library is used to support pagination
 - the AssetCollection has been refactored to extend
   Backbone.Paginator.requestPager so that it can be paged
 - an abstract PagingView class has been added to generalize
   the communication with a paging REST API
 - the AssetsView has been reimplemented to extend PagingView
 - two new child views have been added:
   - PagingHeader: the paging controls above the list of assets
   - PagingFooter: the paging controls below the assets
Add myself to list of authors
Assign valid content_type to static resource (import_static_content)
STUD-878
Merge pull request #1912 from edx/andy/asset-pagination

Add pagination to Studio's Files and Uploads page.

These changes are for STUD-813.
Added django commands to get statistics and repost submissions to grader for open ended problems.
ORA-286
Merge pull request #2076 from edx/brian/server-track-null-request

Modify server_track to handle being called without a request.
Don't catch all exceptions.
Merge pull request #2082 from edx/ned/dont-catch-all-exceptions

Don't catch all exceptions.
Merge pull request #2001 from edx/waheed/openended-problems-commands-2

Django command to post submissions to ora
Fix URI vendor module to be referenced via a relative URL.
Update JSInput info with feedback from Jean-Michel

Add more specific info about HTML+CSS+JS files, SOP
Merge pull request #2085 from edx/andya/asset-pagination-fix

Fix URI vendor module to be referenced via a relative URL.
Update index

Remove javascript_input and create_lti; add tools
Merge pull request #2023 from edx/sylvia/documentation/BLD-619

Add info about template for Checkbox problem type
Merge pull request #2075 from zubair-arbi/zub/bugfix/std878-wrongcontenttype

Assign valid content_type to static resource (import_static_content)