Ubuntu: Implements PasswordWatcher for imap access

Now uses the passwordWatcher. When authRequest signal is
received it either auto connects or if no password saved ask
user to enter password.

REVIEW: 118130
BUG: 333965
BUG: 332987

Removed using an anonymous function to call a reloadPassword slot
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.

REVIEW: 118355
Ubuntu: Add licence header to HeaderComponent.qml

REVIEW: 118430
BUG: 335597
Do not call that function when setting up signals & slots

CCMAIL: dpniel@ubuntu.com