Convert plugins to modules

I would like to propose changing the structure of Dynamic Render. I would propose doing away with the concept of plugins and instead implementing Dynamic Render renderers as plugins.

The reasons:

1. Take advantage of Drupal's existing module infrastructure, including installing, version tracking, and database support
2. Ease the path maintenance headaches presented in cases such as sIFR 2 and sIFR3, where file names conflict.
3. Remove the requirement that all renderers be accepted into the official Dynamic Render project.
4. Keeps the codebase size of Dynamic Render down, which in turn will simplify the release cycle. Otherwise, for every new renderer, there is that much additional work which must be done before this module can be released.

The proposed architecture:

For a first cut, most of the existing rendering infrastructure will remain the same. Renderers will still implement an info hook and some rendering hooks. But the path-specific code (that requires where the plugin should be) will be abstracted out. Each renderer module will be required to know where its own files are.

Some reconsideration of the hooks that perform rendering might be necessary. Not all renderers support single-stage rendering. Some require setup to occur at one point and rendering to occur later. (e.g. sIFR 3)

Matt