Refs #7178. Do a minor refactoring.

Instead of going through a huge pain of calculating average of time
series manually (from a string!) we can just use an appropriate
method.
Refs #7178. Change property not found/set messages.

It is not an error when expected log is not found or set.
Refs #7178. Use ostringstream to build info string.

Concatenating strings is inefficient and tedious.
Refs #7178. Add code to display new properties.