Small improvements to tool data API.

Update tool data API to use newer API decorator for better error handling, create some abstractions for reuse down stream, etc...
Implement a detailed break down of data table fields via API.

Originally this approach was laid out by Kyle Ellrott in this pull request (https://bitbucket.org/galaxy/galaxy-central/pull-request/531/add-downloads-to-tool-data-api/diff). The changes to galaxy.tools.data are entirely his contribution, I only reworked the API and endpoint slightly and did some stylistic fixes and refactoring.
Allow downloading index files via tool data API.

This provides direct access to the files to admins - probably still wise to provide some mechanism to download a copressed archive of these files.
Allow specification of multiple data manager configuration files...

... use this to create API functional tests for data managers.
Implement test case for Pull Request #577.