[Geary] Add an option to alway use separate composing window

[Pétùr <peturvilj gmail com>]

Suggestion: Geary should add an option to alway open new emails and replies in a separate windows. (or correct the problem like suggested in the last paragraph)

I have a small screen (14'). Every time I want to reply to a email inside a thread, Geary creates the new email in the bottom right of my screen. If I want to reply point by point with in the text quotes, I have to scroll down and recenter the message. This is pretty annoying. 

When you reply, the original email in inside the new mail. So the new mail should take all the space in the right panel. It shouldn't be at the very end of the right panel.

bye