[Geary] composer icons

[Federico Bruni <fede inventati org>]

Hi folks

I've always felt that some of the composer icons are not much pretty and, more important, you cannot easily guess what they do at first glance.

The latest introduced, the dictionary icon, looks nice and now the difference with the rest stands out, in particular with the quote icons and also the link icon.

Where are these icons taken from? Can we use something else? For example:

http://fontawesome.io/icon/quote-left/

http://fontawesome.io/icon/link/

I could find only this related issue:

https://bugzilla.gnome.org/show_bug.cgi?id=713905