Add concepts for exercises

[brollb]

It would be nice to include concepts for exercises like HoFs, iteration, variables, etc.

What would be the best ontology for this? We could use something based off of AP CSP perhaps...

[brollb]

One easy way to do it would be to define concepts based on the blocks in the parsons problem. This would allow them to be added automatically from the parsons.xml file. Concepts could be defined like this:

• Iteration/Loops: loop blocks
• Lists: reportNewList (or any other list block)
• Conditionals: if, ifElse
• Networking: callRPC, message passing blocks
• Recursion: (special case)
• Higher Order Functions: ring blocks, map, combine, etc

[brollb]

Basic concepts can be provided to the metadata.toml file so I am closing this and making a new issue for determining this automatically