Convert external electric fields from MML

[#52998997]
Change conversion of electric fields from MML

[#52998997]

Simplify original implementation from Classic MW. Assume that
intensity is always > 0 and set orientation accordingly. Classic MW
does it in its internals, but that causes that serialization is weird.
Implement external electric fields support in MD2D

[#52998997]
Let users set and get electric field properties using Scripting API

[#52998997]
Update "Electric Field" interactive

[#52998997]