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: Modify cmake for click packaging and run on device

- Adds a new option UBUNTU_CLICK_MODE for use when either running
  trojita on device from QtCreator or building click packages.
  This option installs trojita to a contained location.

- Removed QCommandlineParser options from src/Ubuntu/main.cpp
  For some reason UbuntuTouch/Unity8 require --desktop_file_hint
  and --stage_hint to be passed when launching an app. Which
  the commandline parser was blocking these args. Since the
  commandline options were only really just setting the size of
  the qquickview we can safely just remove it and stick to a fixed
  size window.

- The click package manifests are located in qtc_packaging/click_ubuntu

- There is an additional trojita-ubu.desktop file specific to
  Ubuntu click packages

REVIEW: 118429