Support plugins that collect package configuration

[ekstrand@…]

It would be nice if Bitten supported package configuration collectors, located by looking for some setuptools entry point. These plugins would inspect the environment and detect particular packages and add the relevant information to the Bitten slave configuration.

I find myself wanting this when I want to test on different Java VMs. Currently, I define a Java package in my config file:

[java]
vendor=sun
version=1.6

It would be very useful if I could write and deploy a plugin that looks for the java program and automatically builds this configuration. With a plugin, this could then be generalized to automatically pick up versions for many other packages (Python, Maven, ...).