WIP: Performance testing of asset metadata in course import/export

First iteration of code which tests performance of asset metadata during course import/export. Uses external code_block_timer module. Also, add script which validates XML file against an XSD file.
Not intentional. I created this module outside of edx because I wasn't sure of the approval process for adding a new module to edx. I don't intend to keep ownership - I instead will do whatever the standard process specifies.

The main point was to create the module outside of edx-platform.