Add "The Double Helix" jsmol interactive draft

[#60966932]

All controls and right model, no actions yet.
Implement all actions / scripts in "The Double Helix" jsmol interactive

[#60966932]

FIXME:
Two scripts breaks the jsmol model so they are commented for now.
Also background color has to be set by hand.
Use new 'molecule' property in basic jsmol example

[#65650786]
Fix model url in "The Double Helix" interactive

[#60966932]
Lock backbone version to 1.1.0, as 1.1.1 breaks Lab build process

[#65963204]
Add interactive presenting two JSmol molecules

[#65652800]
Add interactive from Lawrence Hall
Use jsmol embeddable page deployed on S3 (instead of github pages)

[#65204022]
Change FF27 warning message

[#65464560]
Fix JSmol scripts in "The Double Helix" interactive

[#60966932]

"exit;" was halting any previous still-running script.
Change iframe model width & height to aspectRatio, update interactives
Fix typo in name of group
Chang px to em for better scaling
Fix unwanted iframe model reload when some dialog is opened

[#66050772]
Create JSmol curricular interactives folder and move DNA model to it

[#66069902]
Add "The Porous Membrane" interactive draft

[#66159290]
Add "Electron Geometry" interactive

[#66159526]
Add "Unshared Electrons and the "Bent" Shape" interactive

[#66159624]
Fix JSmol embeddable URL

[#66159624]
Add "An Atom's Energy Levels" interactive

[#66159426]