Rebase into multi. parameters.
Add example tool with task splitting to tool functional framework tests.

Enable task splitting in functional tests to test this. Specify tool_dir in samples tool_conf.xml so it doesn't need to be explicitly set in scripts/functional_tests.py.
PEP-8 and style fixes for various files related to history import/export.
Move some history export logic out of controller into model...

For reuse by API.
Refactor history export functionality into ExportsHistoryMixin...

... for reuse in API.
Refactor history import functionality into ImportsHistoryMixin...

... for reuse in API.
Add new API decorator for raw downloads.
Implement history exporting via API.

Two new routes one that can be PUT against to poll for download_url and one to fetch a completed download via a GET. Includes simple test case. This doesn't cleanly map to REST to my mind so I have hobbled together this approach, happy for further input.

Good reading:
https://restful-api-design.readthedocs.org/en/latest/methods.html#asynchronous-requests
http://stackoverflow.com/questions/4099869/is-it-wrong-to-return-202-accepted-in-response-to-http-get
Implement history import via API.