Bug 27816: "Click to edit" in Point of sale is untranslatable

Bug 27816: "Click to edit" in Point of sale is untranslatable

This patch adds an option to the Point of sale jEditable configuration
to explicitly set the title attribute to "Click to edit." This will
allow the string to be picked up for translation.

To test, apply the patch and test that the correct string is
translated. In this example I'm testing fr-FR:

  - Update a translation:

    > cd misc/translator
    > perl translate update fr-FR

  The "Click to edit" string should already have been translated, so
  it's not necessary to update the .po file.

  - Install the updated translation:

    > perl translate install fr-FR

In the staff interface, switch to the language you're testing and open
the point of sale page. Add some items for purchase. They should appear
in the "This sale" table. Hover your mouse over the values in the "Coût"
and "Quantité" columns. You should see the translated string, "Cliquer
pour modifier."

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
(cherry picked from commit 126326b8b3933cd64f8ddf34ad96fd69f3db3d0e)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>