Add skeleton for demo programs

We'll use demo programs to test and help implement new and existing
features within buxton, they are not intended for general use.

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