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

common/lib/xmodule/xmodule/templates/about/overview.yaml

common/static/images/placeholder-faculty.png

common/test/data/2014/about/overview.html

common/test/data/course_info_updates/about/overview.html

common/test/data/manual-testing-complete/about/overview.html

docs/en_us/platform_api/source/course_info.rst