Extend example/points

[cburstedde]

Description

The example/points directory is relatively ancient, but still instructive. It has been written long before the present search capabilities have been added to p4est. To make it run, it requires a binary file with a set of points. These are currently not in the repository. In addition, it would be fun to write an alternate implementation that relies on the functions in p4est_search.h

Proposed solution

• Add a few point files to the example/points directory to experiment with.
• Write a second program that reproduces the functionality using mesh searches.