Update icon font to Font Awesome 5.0.2, search support

Adds support for icon search. This saves a lot of time since user
doesn't have to search visually through all icons. User just types some
text (search terms are retrieved from font's metadata; like "clipboard",
"left", "next" etc.) and non-matching icons will be hidden.

In icon selection dialog, brand icons are at the end of list and have
slightly different background color.

Few icons are missing.