Highlight which odk questions / groups / choice lists can be localised

[dave-mills]

We need a generic approach to identify the places in any given ODK form that should be reviewed for localisation.

The options for localisation of existing parts of the ODK form are:

For this issue:

1. The label or hint of a question (survey row - editing a LanguageString linked to a SurveyRow)
2. The items in a choice list (choice lists - adding/removing ChoiceListEntry items linked to a localisable ChoiceList)

For future issues:

4. The constraints of given questions.
5. Entire question groups (like the diet quality module)

The constraints are more complex, so we'll address them in a separate issue.

For entire question groups - for HOLPA, we can probably do the simpler thing of making each question in the group localisable. For longer term, we need to highlight when certain "modules" (or question groups) are fully localisable, e.g. the PPI is a standardised survey module that has different questions for different countries.

For this issue, we need:

1. A documented approach to identifying localisable labels, hints.
2. Added script to mark those items as localisable when the SurveyRow and ChoiceList entries are created (from an XlsformTemplate)
3. For xlsform template management - admins should be able to see which questions + choice lists are customisable for a template.