** Create a new command

This command works like phinx status, but with a difference, it print on the screen a json object like this:

[
{"status": "up/down", "migration_id": "", "migration_name" : ""},
{"status": "up/down", "migration_id": "", "migration_name" : ""}
]

Motivation to do this: Sometime u execute phinx in a CI tool or in a Deploy script and with the default output it´s hard to get the list of migrations.
Remove the statusjson command and create a new argument -f on the status command wich print on the screen a json object with the migrations.
Add the default value to $format argument in the Manager::printStatus() method.
Adding Unit Test to Status command and format argument.