Remove print commands

[BenediktSeidl]

Not sure about the second commit, open for discussion.
I'm still a nix newbie and did not understand the :p command.

[jonringer]

It's more that nix is lazy, so when you have a "thunk", it just shows the outermost structure. The attrset example don't look particularly great when you just get { ... } as the return value.

[jonringer]

That said, there may be an argument that we could just have nix repl opened with strictness turned up (not sure if this is a thing, but nix eval has --strict)