- Positioning was calculated using `boundingRect` while `transformOriginPoint` was set according to `tightBoundingRect`, causing mismatch when `QGIDatumLabel` contains more than text (eg. shapes around text). Now `transformOriginPoint` and positioning calculated according to `tightBoundingRect`, and setting `transformOriginPoint` of `QGIDatumLabel` are handled by itself. This fixes an issue where the gap between dimension lines and text varied depending on dimension's angle.
- `m_lineWidth` was set in multiple locations, causing confusion and bug introduction
- If `X` or `Y` property changed, the remaining changed properties were not handled due to using `if else` rather than `if` for property change checking. This became an issue due the above mentioned simplification of `m_lineWidth` setting: if `X` or `Y` had changed (upon document restore).
- Center position was uneededly saved in variables `posX` and `posY` when it could be calculated on demand using `tightBoundingRect`. Removing this uneeded state simplfies code and lowers the risk of bug introduction due to lack of updating state.
