Add CLI Interface

[steveway]

Since we have some neat functionality now with the automatic recognition using Rhubarb or Allosaurus, we might want to offer a CLI Interface.
It should not be too complicated to add some options with argparse.
So for the functionality there are a few things like:

• Load supported Project files and Sound Files.
• Export of specified Voices with the supported Export options.
• Applying Autodetection using Allosaurus or Rhubarb with extra options for these.
• Saving as one of the supported Project files.

Maybe also allowing to select directories containing multiple files so that the user can apply all the steps to several files at once.

This way a user could then create several files for his project.
Example:
A user has a folder containing some sound files for an Animation or Game Project.
He wants to create some .json files for them to use in his project:
papagayo-ng.py -i /path/to/files/ --use-allosaurus --export=json -o /path/to/save/json
This would then open the files in the directory one by one apply allosaurus with default settings and export the result to the output (-o) directory.
Something like this maybe.

[steveway]

I've begun some work on this on a new branch here: https://github.com/steveway/papagayo-ng/tree/cli_test