demos: Add timing demo

This demonstration simply sets the same key and value 10,000 times
and reports the total and average times for this operation. Note
that debug should be disabled before performing this test, because
constantly printing to the terminal will drastically reduce performance
and is an unfair indication of Buxton performance.

Signed-off-by: Michael Ikey Doherty <michael.i.doherty@intel.com>