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.

[cburstedde]

Relating this to #211.

[cburstedde]

Point files are now generated on demand using an auxiliary program. We may still want to diversify the point structure depending on the connectivity to be used.

It will still be fun to replicate a second example that is based on search. This may wait, however, until we have formalized and implemented a generic search-based refinement algorithm.