Added interactive mode in charm4py (BETA)

#1

Interactive mode beta was just added to master.

This feature will be part of release 0.11

Interactive mode is similar to an interactive Python shell with the main difference that it runs in the context of a charm4py job involving multiple processes. It is possible to define new chare types, create new collections of chares, call remote methods, etc.

This feature is in BETA. Please provide feedback and suggestions.

NOTE: Currently this only works with charmrun on only one host. For example:

python3 -m charmrun.start +p4 ++interactive

will launch an interactive shell using 4 processes.