Simplified topology configuration

* Emitters are easy to reuse and configure - all properties set during topology initialization are preserved
* Multiple emitters per python module
* No more emitter-per-module file structure
* No module-level run() method required
* Python package support (python module creating topology still must be on the root level)
* ____init____ are optional

https://github.com/bonya/Petrel/wiki/Simplified-Topology-Configuration