Minor: indent
#885 "Universal send button"

- ProcessButton
  - implements configurable processes
  - converted most buttons to new mechanism
  - new FR properties defining default processes
  - buttons use Bootstrap icons
  - icons are defined in resources
  - fr-persistence-model greatly simplified
- XFormsAPI supports new actions
  - dispatch
  - send (XFormsSendAction in Scala)
  - toggle (XFormsToggleAction in Scala)
  - rebuild, recalculate, revalidate, refresh
  - show (XXFormsShowAction in Scala)
  - load
- FormRunner: more convenience methods
- XFormsModel: Scala base class
- XFormsModelSubmission: Scala base class with native listener support
- other refactoring and renaming for clarity