UX improvements (from HN)

Some UX improvements:

There is no useful coding workflow. Thats how I do it: CTRL+o, enter filename, write some code, ESC, CTRL+ENTER, CTRL+UP, ENTER, oh an error, CTRL+o, enter filename, .... That is a little bit tedious.
Without syntax highlighting, typos occur everywhere :)
If there is an error in a script, the stacktrace shows a line number. But the editor does not have line numbers, so I have to count it manually. That sucks.
Switching between modes would be nice. So switching from the mail view to the editor an back again (with the file and the mail opened) would be nice. A lot of time, there are some bits an pieces in the mail which are relevant in the flight mode or in the editor (station names, some hints etc.)
I've crashed the game and brought it to a point it can't be played any more. (https://p.fu86.de/1468240067-8920.png) (I think I've done ship.docs.msg1 = dofile(...), which caused the problem). Even if I wipe the savegame and use the stock config, the game crashed again after a few seconds.