"not self.title" doesn't work because of "self.title = title or """

changes ln from third to first form (see man ln)

This was a remnant of LuCI that was never used in gluon-web.

Replace the ugly arrow shown in Firefox with a custom SVG arrow. Tested
and working in Firefox, Chrome and Edge. The arrow doesn't show in IE, but
the gluon-web-model JavaScript is already severely broken in IE, so we
don't care.

- Add a dependency array to section template
- Lift dependency handling from AbstractValue to Node
- Split resolve_depends() into a function handling dependencies of a
  node itself (resolve_node_depends()), which now is used for all nodes,
  and the existing recursive descent through the node tree
- When any node's dependencies are not satisfied, all descendents are
  reset recursively, meaning that an option in a section that is hidden
  will always be ignored, as if the option's own dependencies were
  unsatisfied

Fixes: #1349

This is currently unused in our packages.

Register to 'reset' event on form element and make call to 'update' function
delayed in 'data-update' handler to allow the form values to update beforehand.

When using a form's 'reset' button, form field visibility was not updated.
This could lead to situations where a checkbox had to be toggled again
twice to display the detail text inputs. (Example taken from private
wifi package)

Also bring back gluon-web-theme's i18n strings.