engineexplorer: Improve TreeView
- Implemented more tooltips for cells (in case the text is truncated),
- Moved "Type" column in front of "Value",
- Implemented recursively expandable sub-trees for lists and maps,
- Lists with only one item are now clearly distinct from a key of an inner type,
- Combined DataSource and Key columns into one and widen it up.
Custom data type
|List with 1 item|