Improve nodestore benchmarking:
* Use more succinct while loops on NodeFactory.
* Better formatting of multiple test results.
* Updated benchmarks.
* Use simpler and faster RNG to generate test data.
Require the master key when performing certain operations (RIPD-666):
* When disabling the use of the master key; or
* When enabling 'no freeze'.

Additionally, a small fix in the handling of 'sfMessageKey' which
would prevent the field from being unset, and some small cleanups.
[FOLD] Require master key to set NoFreeze
[FOLD] Fix missing 'else' when handling sfMessageKey
[FOLD] Cleanup handling a little bit
[FOLD] Regular key can disclaim freezing if master key is disabled