Support more variant types

[cyndis]

Floating point types and variant lists, at least.

[liamsi]

If you are also interested in bool variant type. I could clean up my branch (from examples and) create a pull request: https://github.com/Liamsi/qmlrs/commit/c9356c814b8dd225783e225dd887f21d5617cf8a Thanks for your great work!