Add a line up behind for departures#57

Add the ICAO ‘behind the departing (type/traffic) line up and wait behind’ command

In general a line up in sequence would be nice, considering this is used in quite a lot of IRL airports (at least in the EU). Great example is EHAM, where they basically always use it to allow less communications to be made.

Line-up in sequence is incorrect phraseology though, so this shouldn’t be added. Fortunately, it is very, very rarely used in real life, except for a few locations with poor RT discipline (due it being incorrect and a huge safety risk).