Add ability to navigate between prompts

[gnunn1]

The intent of this feature is to allows users to navigate between the previous and next command prompts using an appropriate shortcut. The idea is that you often want to see the results of the previous command and scrolling through the terminal buffer can be annoying if you are dealing with long output. By hitting the shortcut one can quickly navigate between command prompts similar to OSX's terminal.

Like OSX's terminal this feature works by simply tracking when the enter key is pressed. This feature will require the alternate screen patch that is also used for triggers since we do not want to record the prompt position when using applications like vi, emacs or nano.