Merge pull request #6435 from edx/markhoeber-remove-unused-files

docs/en_us/shared/exercises_tools/annotation.rst

docs/en_us/shared/exercises_tools/checkbox.rst

docs/en_us/shared/exercises_tools/chemical_equation.rst

...n_us/shared/exercises_tools/circuit_schematic_builder.rst

docs/en_us/shared/exercises_tools/conditional_module.rst

..._us/shared/exercises_tools/create_exercises_and_tools.rst

docs/en_us/shared/exercises_tools/custom_javascript.rst

docs/en_us/shared/exercises_tools/custom_python.rst

docs/en_us/shared/exercises_tools/drag_and_drop.rst

docs/en_us/shared/exercises_tools/dropdown.rst

docs/en_us/shared/exercises_tools/external_graders.rst

docs/en_us/shared/exercises_tools/full_screen_image.rst

docs/en_us/shared/exercises_tools/gene_explorer.rst

docs/en_us/shared/exercises_tools/google_hangouts.rst

docs/en_us/shared/exercises_tools/iframe.rst

docs/en_us/shared/exercises_tools/image_mapped_input.rst

docs/en_us/shared/exercises_tools/index.rst

docs/en_us/shared/exercises_tools/lti_component.rst

docs/en_us/shared/exercises_tools/math_expression_input.rst

docs/en_us/shared/exercises_tools/mathjax.rst