OppositeLen HTML implementation

See merge request !2

Use custom html elements that have only the slot / solution id and replace them in UFrameIT with the actual data, because I can't fill in the data-fact-id from here without larger code chages.

This reverts commit 96aa5ca9.

This reverts commit 8acd9e9c.

Added additional conditions for construction:

Square: Distance AB and Distance BC, so that inuitively the area is dAB * dBC.

Circle: The distance from thew center to the edgepoint, also for providing a more intuitive way to construct circles.