Implemented status on reminders, both extended reminder model and added f...

...unctionality to the controller that modifies a specific events color.
Rather than "completed", the Android app sets the `acknowledgement` field to "OK" which matches what the button on the reminder notification says. I believe we have a story which relates to having different types of responses where rather than "OK" the Android app would set it to whatever the other responses that type of reminder had.