Changes to samples.xml, adding documentation, reordering for clarity.

Cleaning up samples.xml.   Changes are done as small commits and should make this file easier for people to gather information.
These items are also test cases for me.
So, I want to keep readability on Preferences.
(The multi-line description will be joined with the next item and  it is difficult to read.)

I'll merge your changes and put some blank lines.