chat pane design

[bill-auger]

feature of epic #31

the "Chat" pane currently overlaps exactly with the "Preview" and "Config" panes when in active mode

the chat pane includes the following passive widgets:

• chat history textarea - (incoming chat text)
• chat entry textbox - (outgoing chat text)

the chat history textarea also hosts the "ChatList" pane within (currently passive) - because the "ChatList" pane is currently coupled to the "Chat" pane it should probably not be a separate issue unless it is decided that it would be useful without the chat