Split out protocol-specific implementations.

Which lines up nicely with Thinking Sphinx releases. Let's pull support for TS v1, v2 and v3 into a single gem.
Support all Thinking Sphinx versions.
Pass the identifier through when configuring.
Use appropriate configuration/settings.
No need for SphinxConfiguration any more.
Uploading configuration from file uses the controller.
Require the Railtie when lazily loading Rails.
Rails 2 support