Ubuntu:Add Click pkg manifests and change cmake to build click pkgs

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

REVIEW: 118429
Ubuntu: modify TrojitaVersion to configure version in manifest.json

Adds an CLICK_MODE option to TrojitaVersion.cmake which if true
will configure manifest.json on each build

REVIEW: 118429
Ubuntu: Remove 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.

Removed associated context properties from main.qml

REVIEW: 118429
Ubuntu: Modify main.cpp to find main.qml in click package

With click packages the qml dir does not fall under a 'standard'
location. So it first looks for trojita.json in the root of the click
package, once that's found we can then descend to main.qml from
there.

REVIEW: 118429
Ubuntu: add UBUNTU_TARGET_ARCH option to cmakelists

This is to stop the need to depend on dpkg-architecture being
available, and keep it so that Ubuntu build can be compiled on non
Ubuntu builders. This is purely for Click packaging which is done
post install to ensure the gnu-archtriplet is correct within the
click package.

REVIEW: 118429
Ubuntu: add README.ubuntu for build/install instructions

REVIEW: 118429