MA-1416 Created a TypedFileUploadParser that validates the mimetype and then takes the content and puts it on request.FILES['file']. Subclasses the existing FileUploadParser. Use namedtuple in IMAGE_TYPES as per style guide: https://github.com/edx/edx-platform/wiki/Python-Guidelines#classes-vs-dictionaries
* Fix paver violations to stablize edx-lint update * Parens, Line2Long * Fix missing docstrings * Fix PEP8 issues * Address PR feedback (thanks @nedbat!)