This adds isNullOrEmpty string helper that cheks if string is... well
null or empty. It is done to improve readability of the code and better
express intent.
Neither in #18332 nor in any of the referenced issues a reason is given why the placement of the coordinate axes must be changed.
Only doing it to make the client code look more consistent is not a valid reason.
This change breaks forward and backward compatibility and with #18717 we already have a hard to solve issue. Furthermore, at this
point of time it's not even clear what other collateral damage the change may cause.
So, this commit hides all the implementation details of the DatumElement and restores the original placement for the axes.
This commit makes the line migration code obsolete
Add the methods DatumElement::getBasePoint() and DatumElement::getDirection() to hide implementation details and guarantee consistent behaviour.
Using the methods fixes several regressions in:
* Constraint::getDirection
* PolarPattern::getTransformations
Most of App::Origin is moved into this sub class of App::Origin.
Add App::Point. Change graphics of the planes/axis.
Remove scale-by-content behavior and make it fixed size on screen.
