libhawaiishell: Add shell handler setting

Make the shell handler configurable, although in the future we'll rely
on a smarter mechanism (change shell handler according to input
devices).

Issue: #122
desktop: Willing honor settings

For now the shell is changed with a setting, it's easier to test but in
the future a more sophisticated mechanism will be implemented.

Issue: #122
tablet: Say hello to the tablet shell

For now it's just a copy of the desktop shell with a two panel layout.

Issue: #122
client: Print a message when the shell handler is changed

Issue: #122
client: Switch between shell handlers

Switch logic done.

Issue: #122
libhawaiishell: Add lookandfeel type to the package macro

This is the first step towards look and feel plugins.

Issue: #122
lookandfeel: Add standard look and feel plugin metadata.

Not much here, just the metadata.

Issue: #122
client: Rename LockScreenWindow to LockScreenView

This is going to be a view much like desktop and panel views.

Issue: #122
client: Remove useless code from ShellManager

This code is not used anymore.

Issue: #122
lookandfeel: Move lock screen here

Issue: #122
libhawaiishell: Add look and feel setting

Issue: #122
lookandfeel: Make lock screen work

We don't have a Background component anymore, replace it with a noise
background until we can load the actual lock screen background.

Issue: #122
client: Simple look and feel loading mechanism

For now we always assume that only the standard look and feel is
available. As soon as the package concept is introduced, a better
mechanism will be implemented.

Issue: #122
client: Actually close lock screen when the session is unlocked

Call the right method to close the lock screen window.
server: Disable screen saver by default

From now on screen savers will be disabled by default, however the
Weston plugin doesn't read settings yet. This means that until settings
are picked up, screen savers will stay disabled.
libhawaiishell: Add package and package structure

A better way to access package contents.

Issue: #122
Disable deprecation warnings

We just included some code from Plasma which uses deprecated stuff,
silence warnings until it is fixed.
libhawaiishell: Package structure definitions

Define structur for the currently supported packages.

Issue: #122
libhawaiishell: Add missing headers

Issue: #122
libhawaiishell: Say hello to Corona

Corona keeps track of all elements in the scene.
For now it holds the QML engine and package information.

Issue: #122