Outline: be able to collapse/expand all entries
This commit adds three new context menu actions to the Outline tree view:
- Collapse all tree
- Expand all tree
- Expand all under this element
Number 3) is like 2) but restricted to the children of the currently selected row. We insensitivize this action in the menu when the current element does not have any grandchildren.
All three actions properly update the metadata
keys index-expand
and index-collapse
so the
state of the tree view is kept and reinstated
in future Evince invocations.
Fixes #736 (closed)