Qt 5.7 cloud part now available

[Timo Jyrinki]

Hi!

I started experimenting with bringing upstream Qt as is as a cloud
part. I can happily announce an early let's say "alpha" version of it
is working and available with "after: [qt57]".

This is not the "qt-ubuntu" I've a vision of as being available via
content interface, but rather building upstream Qt as part of your
app. This is only worth considering if you absolutely require a newer
Qt than what is available in Ubuntu (5.5 in Ubuntu 16.04, 5.6 in
Ubuntu 16.10, 5.7 somewhere Jan-Feb in Ubuntu 17.04).

For fun, you can try out a dummy QML test app (C++ backend included though) by:

sudo snap install --edge timostestapp2
timostestapp2

Mind the missing font for Chinese characters, it's not a bug, just a
font not staged :) What it's really about is that it is a simple
application that happens to bundle and uses upstream's to-be-released
Qt 5.7.1 built with the cloud part.

Included Qt modules: Qt 3D, Qt Bluetooth, Qt Base (Core, Gui etc), Qt
Declarative, Qt Tools, Qt Web Channel, ... and a lot more, but _not_:
qtwebengine, qtwebview, qtwebkit. Also no Ubuntu UI Toolkit yet, we
haven't started testing it with Qt 5.7 yet.

You can use the snapcraft.yaml, launcher and modified parts/plugins
from https://github.com/tjyrinki/timostestapp2. Modified autotools
plugin is for building Qt (it doesn't seem to fetch that from the
cloud part, that would be nice), and modified qmake plugin is for
building your app. No CMake plugin or such yet, this is very much
"yay, it runs now!!" first version done in-between all my other tasks.

-Timo