Bug 1034600 - [Messages] Suggestions list is badly located. r=julien

* Recipient suggestions container moved to more appropriate place;
* Recipient suggestions now occupy all possible space minus heights of the app header and message "To" field.
* ```.contact-list``` styles are cleaned up a bit.
Left it for now, because with ```width:100%``` and ```box-sizing:border-box``` instead of this I see blinking ```borders``` for the contact lists when scrolled to end position, but continue to drag with finger so that list is scaled. 

Still trying to understand what is this.