No warnings

This branch removes a lot of warnings generated by vala, mainly for missing try-catch-clauses making the output for errors a lot more readable.

It also fixes the queue_relayout warning, which was in LineView.vala, because of the allocation change inside the allocated_changed callback.

I've also made FinalTerm exit with a warning when either the color scheme or the theme is not found. Otherwise, for the theme at least, it'd just exit in an confusing floating point exception. Maybe trying to load the default theme, if the requested one, fails would be good too.