Python LWRP for multi-tenant installs.

Users that deploy multiple Python apps on the same machine need to be able to do something like:

``` ruby
appdynamics_python_agent "/path/to/virtualenv"
```

to install the AppDynamics agent into each virtualenv that will be monitored.

Start by inspecting the cookbook's existing Python agent installation resources and how custom resources are structured. Add support for an appdynamics_python resource that accepts a virtualenv path and installs the agent into that environment; done means multiple virtualenvs can each be configured independently.

Written by the indexing model from the issue text.