Bug: workaround to prevent allocation cycle.

A proper implementation would probably require to write a layout manager or
write the parent actor allocation functions. Not sure why there is the
allocation cycle in the first place. Upon allocation of actor 'b' I change
actor 'c'. both 'b' and 'c' are children (not directly) of a common parent 'a':

a > b, c

This is just a workaround of the problem.
Makefile: manage extension version.

An optional VERSION variable can be passed to the make command:

make [install | zip-file] VERSION=27

This updates the corresponding metadata and appends the version to the
generated zip-file. If no version is provided, the version in metadata is set
to the SHA1 of the current commit.
Update translations: use only language names instead of full county codes.

Not sure which is the right way. I use the language name instead of the language_country format for language whith only one country associated or for the main country.
Update translations file Language header field.

Avoid WARNINGS.
Include adwaita-theme into the extension.

Since probably Gnome-Shell 3.8 extension theme can overwrite default values.
There is no need anymore for a dedicated theme. I import it here and
enable/disable it by controlling a css class.
Add settings for the theme customisation.
Remove option: always apply custom opacity.

Remove the option to apply custom opacity only when in autohide. If custom
opacity is set always apply it.
Add DashSlideContainer Actor.

A simple Actor with one child whose allocation takes into account the slide out
of its child via the _slidex parameter ([0:1]).

This is required since I want to track the input region of this container which
is based on its allocation even if the child overlows the parent actor.

This will solve the problem with multimonitor where the slided out part of the
dash even if invisible due to the clipping still steals input events. Hopefully
it will also help to simplify the code a bit.
DashSlideContainer: set width when fully slideout to 1px.
DashSliderContainer: add paramater for slide direction.
Use DashSliderContainer. Code cleanup.

Start to use the new DashSliderContainer. This should solve the bug concernig
stolen clicks with multimonitor-configuration and primary monitor on right. The
code has been partially cleanup with reorganization of the dash constructor.
Some code is not necessary anymore with the new container such as the clipping
function and the Clutter.Gravity machinery and thus has been removed.
DashSlideContainer: add initial slide parameter.
Track only the  input region  of DashSlideContainer.

Probably after a rebase, I end up being tracking the inputregion og the _box
and dash._box actors instead of that of the slide, that exists exactly to be
tracked. This makes the area behind the hidden dock when placed on a right
monitor finally clickable.
Makefile: code clean.
Add pressure sensitivity to show the dash.

Add an option to use the pressure barriers and a pressure threshold to show the
dash when available. This also allow to use the autohide in mutltimonitor
configurations with the primary monitor on right. The option is enabled by
default.
Bug: put to zero a timeoutid after executing it.

Avoid warning concerning the removal of an non existig timeout. I think in the
past there wasn't this warning and the remove was just ignored.
Bug: correctly handle dash y position.

After introducing the _slider container, its y position must be taken into
account when computing the staticBox coordinates.
Emit signals for when the dock is triggered to show or hide.

These signals are not used by the extension itself, they are provided for
compatibility with other extensions - notably
workspaces-to-dock@passingthru67.gmail.com - which can thus connect to this
signals to know when the dash is shown or hide.