Add option to preselect nothing when automatic completion is invoked
Since the first entry was previously always preselected, it sometimes made entering newlines (with the return key) hard for users who are not familiar with Shift+Enter.
I think the config entry name AutomaticCompletionPreselectFirstEntry is too long, but I couldn't think of a less verbose name.
Also when this option is enabled, I made the tab key select the first entry instead of doing nothing. I think this also makes this option easier to use since the tab key is easier to reach compared to the down arrow key. However it overloads the function of the tab key so I'm not 100% sure if it's a good idea.
Edited by Jan Paul Batrina