Implement get_pid, respect bundle_id in list_processes and list_bundle_id

[nisargjhaveri]

• Implement a new command --get_pid. Given a bundle_id, prints the pid for the app if running. Returns -1 as pid if not running. Related How to attach to running app #525
• If bundle_id is specified, only list bundle properties and processes for that bundle when used with --list_processes or --list_bundle_id for convenience and lesses amount of transfer and parsing on the user side. Related Add a method to directly get the device path of the app  #524

[gabebear]

Awesome, this is incredibly useful