Form translations

[ciara-mc]

This PR:

• uses an app version of xlsform template extending from the package version
• contains seeders for languages and language string types
• creates template languages, survey rows and language strings when a new xlsform template is created
• shows the user all languages available for the template
• creates an export with one row per survey row - language string type with all existing translations and a space to add a new translation
• creates a new template language and language strings when a completed translation file is added

To Fix

• [x] pass the translation file to the XlsformTemplateLanguageImport

Further Development

• [x] add validation for translation import - ensure no missing transaltions
• [ ] case when template xlsfile is replaced
• [x] enable editing of language strings
• [x] enable picking of language / creation of XlsformTemplateLanguage before uploading translations file

For future PR:

• add instructions in export file/on the relation manager & improve design of export
• multi worksheets - include choices

[dave-mills]

I think that last update works. The step-by-step approach is solid. I think there's a few things to think about on how to present the workflow to users, but that's not for this PR. For me, this works and is a good approach 👍.