Ubuntu: improve OneMessagePage and the displaying of messages

Created TrojitaWebView component, with the webviews flickable disabled.
Delegating flickable behaviour to the page flickable.

Also i have created a new header component which expands and collapses showing
all envelope details. The email addresses are formatted and clickable
emitting an emailAddressClicked signal

dropdown-menu.svg is part of the Ubuntu-mobile-icons package
available from http://packages.ubuntu.com/trusty/all/ubuntu-mobile-icons
and is available under the CC-BY-SA 3.0. Copyright by 2004-2012,
Canonical Ltd.

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