Respect values of new completion options

This has a couple changes:

1. Minor copy edit to the UI pref for console 'automatic' completions
2.  Add `isConsole` parameter to the `RCompletionManager` constructor -- this is necessary for us to respect the 'console automatic' completions option; as it was the option disabled automatic completions both in source and console pane.
3. Respect the 'show signature tips' option.
4. Don't let event propagate on escape when sigtip is showing (this ensures that e.g. if the sigtip is showing in the console and we hit escape, we dismiss the tip without clearing the console)