PropertySheet is changed to derive from PropertyExpressionContainer,
which makes it a link type property that is capable of external linking.
It now relies on the unified link property API to manage object
depenency, and tracking of object life time, relabeling, etc.
This patch also includes various fix and improvement of Spreadsheet,
such as improved recompute efficiency, correct handling of document
label change, etc.
- Refactoring/clean-up of code
- Dependency tracking of aliased cells
- Various resolution errors
- Rewriting of ranges when columns/rows are inserted/removed
- References to aliases keep their units.
