Add a "Display" page to the FBE

Currently, it only allows to toggle overscan/underscan.

[endlessm/eos-shell#3020]
display: Register the resources
display: Set horizontal alignment
po: Add new files to POFILES.in
po: Update POT file
Merge pull request #31 from endlessm/shell/3020

Add a "Display" page to the FBE

[endlessm/eos-shell#3020]
New translations from Transifex
display: Re-read the configuration on toggle changes

Which means don't try to re-apply the same setting.
account: fix GCC warning

We were passing the wrong structure type.

[endlessm/eos-shell#3020]
display: fix GCC warning

Unused variable.

[endlessm/eos-shell#3020]
network: fix GCC warning

Use the right prototype for the sort function.

[endlessm/eos-shell#3020]
display: reload configuration when screen changes

This way, we won't have stale information when toggling the checkbox
again.

[endlessm/eos-shell#3020]
Merge pull request #34 from endlessm/shell/3020

Shell/3020
add ar.SY in the languages list

As when reading the personality file the prefered language is set,
there is no need to add more logic on it.

[endlessm/eos-shell#3351]
set the envvar LC_MESSAGES

When the user sets their preferred language, the environment variable
LC_MESSAGES shall be set too, because gis might spawns processes (e.g.
gkbd-keyboard-display) and they should be localised accordingly.

[endlessm/eos-shell#3172]
display: hide overscan page when we can't get screen or primary output

Instead of showing a label that is probably not very helpful.

[endlessm/eos-shell#3370]
display: hide page when using VGA or not on an HD resolution

Overscan is not needed in those cases.

[endlessm/eos-shell#3370]
Merge pull request #35 from endlessm/shell/3370

Shell/3370
display: change the wording on the overscan page

Include a picture to explain the option instead of text.

[endlessm/eos-shell#3371]
Merge pull request #36 from endlessm/shell/3371

display: change the wording on the overscan page