Add a new shell_out with support for hooks to create async functionality.

[aaronbog]

This pull request contains three main parts.

1. an implementation of the shell called execute.py

• This is a function that only concerns itself with executing commands on the host system
• It facilitates the use of hooks to do additional work without blocking the execution of the program
• The newly returned data type allows for more functionality over the previous implementation

2. hooks

• a way of working with the datastreams from commands
• allows for async logging
• better extraction of data in the middle of using a command
• can be used in a variety of ways and is customizable and extendable

3. a port of the old shell_out functions

• This is backward compatible in functionality (not all logging options are currently supported)
• This can be toggled off instantly should there be any need to revert to the old system