Support for nested data structures

[cher-nov]

This is very related to #1 and maybe even supersedes it.
Also see #4.

For now there's no possibility, for example, to create a vector of maps and then deepcopy it properly, with new instances of maps being created.

[glouw]

@cher-nov , I am building what you are looking for:
https://github.com/glouw/ctl