Add first set of Fablevision SVG images connected with transcription

[#47730529]
Enforce constant model dimensions when DNA is present

[#47730529]

This is very significant, as if model dimensions are too big or too
small, DNA elements can be unreadable. It also ensures that aspect
ratio of the model is reasonable for animation.
Implement Nucleotide class which renders a single nucleotide

[#47730529]
Update genetic renderer to use images for DNA rendering

[#47730529]
Change fontScale property in "Modeling Transcription"

[#47730529]

As this interactive should be used in "large" size.