Add function(s) to execute code on all Python servers

[oubiwann]

Currently, the schedulers determine which ErlPort Python server to execute on. There are situations, however, where one would want to execute a function on all servers at the same time. The following uses cases could apply:

• testing and debugging: making sure that all results are the same, that all Python servers are operational, etc.)
• timing experiments
• operating on random data sets where sequential execution isn't necessary (e.g., generating populations, extracting random samples, running GAs/GPs/NNs)