data mutability, touched database.py

Summary:
 - TaskHandler now makes it easier to modify it's data blob.
 - Removed UTF-8 specific stuff.  Database.py is MemSQL specific.
 - Added tests for unicode and data manip

Test Plan: make test

Reviewers: mandrews

Reviewed By: mandrews

Differential Revision: http://grizzly.memsql.com/D5025