Settings: change Pie controls wording

As stated before, the name 'Pie controls' is well-known
and therefore is being used instead of a more descriptive name.

This change modifies the summary of \'Pie controls\', stating
that they are 'floating controls', as we also need to deal with
users who have not heard about this feature. The title stays the
same.

In other languages this will be reversed: the title will contain
a translated version of the 'descriptive name' and the summary
will contain the original English name, 'Pie controls'.