Sequence of sequence of constant number

[gordonwatts]

Sequence of sequences should allow constant numbers. Write tests to make sure they work.

• [x] Sequence of a constant number
• [x] Sequence calling a function like abs(1).
• [x] Make sure (if possible) that the type system works

Test this using the lambda construct for assigning results to an object.

[gordonwatts]

To get the type system to work, we need to modify datafram_expressions. Issue added there.