fix db and collection operations and returning obj instead of array

[586837r]

cloning the response breaks db and collection instances
not sure if this is a good way to fix it but it works

[586837r]

fixes #37

[jomel]

I was looking into a fix too, and thought it would have been better to check whether 'response' is an array at that point, rather than hard-coding the methods... didn't have the time to do testing as I don't have a working nodered build right now.

Also, this will REQUIRE a docs entry & a full-version bump to 3.0 as this significantly changes behaviour and might break people's flows who have worked around the issue. (node-red won't automatically update a module acoss a major version, but will with a minor bump)