User interface improvements

Under the Send tab when you select a From address the To address is automatically populated if the from address is a chan. This just makes sending messages to chans a less cumbersome user experience.

There are also some minor edits which are just the result of the automatic trailing whitespace removal of my editor.

Also message font type and size is configurable from keys.dat. This fixes a longstanding issue which I've had in that the default 9 point default font is barely readable.