Completed normal task EXT-3397 (Hide well buttons if there are no active IM...

Completed normal task EXT-3397 (Hide well buttons if there are no active IM sessions and unresolved notifications)
* Implemented hiding of bottom tray's wells if there are no active IMs or unresolved notifications (via LLBottomTray::notifyParent)

* Also refactored initializing code to init a pointer to a chiclet panel and map with bottomtray parts in postBuild BEFORE initializing start wells' visibility.

For now minimal viewer width when all buttons are still visible (and have non-truncated labels in the 'EN' locale) with opened sidetray is 1041 px; with short Speak button (without text label) is 990 px. (with implemented patch in https://codereview.productengine.com/secondlife/r/126/)

Each well button takes 37 px (with a padding). So, they can free up to 74 px when invisible.

reviewed by Vadim at https://codereview.productengine.com/secondlife/r/136/

--HG--
branch : product-engine