unify dropdown item font styles

Squashed commit of the following:

commit 2bdba162e403d8020f08106c8121df6bac65bf21
Merge: 33bcd6f f9352ed
Author: Matus Kmit <matus.kmit@zhdk.ch>
Date:   Wed Jul 16 13:03:14 2014 +0200

    Merge branch 'master' into mk_unify_styles_hand_over_dropdown_items

commit 33bcd6f2b7f4e2b5ef9604aa8df92d83c1f3b5c5
Author: Matus Kmit <matus.kmit@zhdk.ch>
Date:   Wed Jul 16 12:11:04 2014 +0200

    reuse $fonts instead of hard coded font family

commit a5fa78f0086a4a8624a6a3837bb6e2ab15162bcb
Author: Matus Kmit <matus.kmit@zhdk.ch>
Date:   Wed Jul 16 12:10:20 2014 +0200

    use same font family for button.dropdown-item