view: minimize parents/children together

view: minimize parents/children together

Minimize the whole view-hierarchy from top to bottom regardless of which
one in the hierarchy requested the minimize. For example, if an 'About' or
'Open File' dialog is minimized, its toplevel is minimized also, and vice
versa.

For reference:
- This is consistent with in openbox, where child views (dialogs) can be
  minimized, but when doing so the parent is also minimized.
- In mutter these types of dialogs cannot be minimized (via client-menu or
  otherwise).
- In both openbox and mutter, when a toplevel window is minimized any open
  children are also minimized.