add code to do localization of the vertical bar-separated portions of
a style's name when displaying the style name and when building the
menu or collapsible browser entries.

Prefixing a name's component with "_l10n_" will request localization
of the text following that tag.

Put all of the camera styles under localized 'darktable camera styles'
and ensure that both that string and 'generic' get localized.

The style quick-access button in darkroom view currently only supports
two-level menus, which is completely impractical when the new
'darktable camera styles' hierarchy runs to hundreds of styles.

This commit generalizes the menu building to go as many levels deep
as the treeview which is built in the styles module in lighttable,
so that the longest style menu is only as many items as a single
camera manufacturer has models.