Implement a notification system

[jacroe]

This is different than what was at #11; that one would have been an action system whereas this will be a displaying of actions taken by other programs on the computer.

Basically, expand the API to allow other programs to ping it with data and somehow display a running list, probably on the home page. For example, notifications that Deluge finished downloading a file or that Sickbeard was updated.

Running list of items that will probably use this

1. Sickbeard and updates
2. Deluge
3. Email sorting (for specific pieces of it, such as Amazon shipment or bank transfer)

[jacroe]

Expand to also actions taken by Alice, things that doesn't warrant a Pushover notification.