Minor: getOrElse
Minor: consistency
Minor: rename, indent
Minor: indent
Implement #635: "fr:grid: add enclosing element and align with repeated sections"

- fr:grid
  - support repeat="content"
  - add enclosing element and align with repeated sections
  - support backward compatibility mode
- Form Builder
  - migrate repeated sections
  - annotate.xpl uses modes
  - insert repeated grids with repeat="content"
  - unify dialog-[section|grid]-details.xbl
- demo forms
  - use `template` instead of `origin`