Group block sets in the tree and follow consistent naming patterns

[arouinfar]

For #76

Currently, there is a lot of variability in how the blocks are named, such as blueMass, primaryMass, set1.1A. The sim view refers to these objects as "Blocks" so let's use that terminology for consistency. I think it would also be helpful to group the block sets together in the tree along with the property responsible for switching between the sets.

Here's a proposed tree structure. @jonathanolson please let me know if you have any concerns or questions.

introScreen
   model
       -blockSets
           blockSetProperty    //property connected to the RadioButtonGroup
           -sameDensity
                +blueBlock
                +greenBlock
                +redBlock
                +yellowBlock
           +sameMass    //use same pattern as above
           +sameVolume


exploreScreen
   model
      -blocks    //only two masses on this screen, so no "sets"
         +blockA    //formerly primaryMass
         +blockB    //formerly secondaryMass
   view
      +blockAControlPanel    //formerly primaryBlockControlNode
      +blockBControlPanel   //formerly secondaryBlockControlNode
      +blocksRadioButtonGroup   //formerly secondMassVisibleControl


mysteryScreen
   model
       -blockSets
           blockSetProperty    //property connected to the RadioButtonGroup
           -random
              +blockA
              +blockB
              +blockC
              +blockD
              +blockE
           -set1
              +block1A
              +block1B
              +block1C
              +block1D
              +block1E
           +set2   //use same pattern as above
           +set3

Edit: I forgot there were references to primary/secondaryMass in exploreScreen.view, so I updated the tree mockup above.

[jonathanolson]

Implemented above, can you verify?

[arouinfar]

Thanks @jonathanolson the tree structure looks good.