Update DataDrivenLearning plugins to add module to sys

[asgibson]

During experimentation it was found that directly including the <module_name>_plugin was not sufficient to use an external package. Instead, it was beneficial to include the entire external package as the module, add it to sys, then create a <module_name>_plugin.Plugin instance. This allows the external Plugin to access its packages modules.

The simple generic_plugin did not experience this effect because it was not accessing any otherwise unavailable packages and it housed within the onair directory structure. Experimental external packages suffered the effect because of their more complex structure.

[asgibson]

This was addressed in #55 and merged with #58