As a desktop client user I want the conversation window to look polished.

The UX for this visual refresh of the conversation window is described in bug 1138445.

Please note that the following are not part of the scope of this bug even if the UX document describes it:
- Minimized view of the conversation window - will be handled separately in bug 1179171
- Ability to add a contact to a conversation from within the conversation window - this will be handled in bug 1179172
- Visual feedback on audio activity for face muted views - this will be handled in bug 1179192

Acceptance criteria:
- Active conversation screen refresh: call control buttons, gear button, remote party face muted indicator, title bar
- Empty conversation screen refresh (Firefox link clicker): call control buttons, gear button, title bar
- Empty conversation screen refresh (Firefox link generator): call control buttons, gear button, title bar, copy/e-mail/Share buttons
- Error message screen refresh: Rejoin button, title bar
- Edit context screen refresh
- Conversation window design applies to link clicker UI
- Popped-out conversation window restyled per UX