Multi frappe instance run simultaneously and other fixes

[Xieyt]

This PR:

• Check for update on PYPI and inform the user. #81
• Provide feature to run multiple frappe sites. #85
• Provided new fm sub command group service which will have restart, start, stop, shell as commands. #85
• Logic to check if the site is created successfully or not, if not then prompt for deletion.
• Logic to create redis workers containers dynamically. #85
• Cleanup all subprocess called processes at exit.
• Improved logic of ports checking, now it will also check if any container running by fm is not taking up the port.