add basic retain parameters to loadModel
revert loadModel modifications
refactor simple loadModel retain parameters
target games retain interactive parameters when loading levels

[#56927054 #54803938 #54867172]
add some reminder comments about the retain parameters hack
merging master into loadModel-retaining-parameters
Merge branch 'loadModel-retaining-parameters'

Closes #54.
draft rutherford experiment interactive

[#57165738]
Add a failing test presenting a bug in MD2D engine (bonds removal)

[#61207522]
Fix removal of radial / angular bonds

[#61207522]
Change error message when atom is moved into the wrong place
Support energy conservation during angular bonds removal

[#58090710]

It isn't the pretties solution, but basically it's necessary for
Chemical Reactions plugin.
Remove related angular bonds when radial bond's atom1/2 prop is changed

[#58090710]

This case is similar to radial bond removal.
Implement .getAngleBetweenVec() function in math utils

[#58090710]
Chemical Reactions: implement early, simplified angular bonds support

[#58090710]

At the moment a constant angle is used, as well as we support only
atoms triplets.

TODO:
- support variable angle value (based on the valence electrons count)
- support configurations of atoms different than triplets
Chemical Reactions: fix a major bug in bonds exchange mechanism

[#58090710]

Basically potential energy increase was calculated incorrectly, what
quite often lead to problems with energy conservation and e.g. could
diverge the model.
Chemical Reactions: add interactive presenting angular bonds creation
Chemical Reactions: update "Hydrogen-Oxygen Reaction" test

[#58090710]

We will create a separate, curricular interactive.
Chemical Reactions: implement correct molecule angle calculations

[#58090710]
ITSI: Dynamic Equilibrium interactive

[#61168894]