The public header files are moved to a new subdirectory, to separate
the definition of the public interface from the actual implementation.
Using an identical directory layout as the final installation has the
advantage that the example code can be build outside the project tree
without any modifications to the #include statements.
Because the sample data contains a timestamp with a limited resolution
of only one minute, there can be consecutive samples with identical
timestamps. To deal with this situation, samples with identical
timestamps are distributed evenly inside the one minute interval. All
resulting non-integer timestamps are rounded to the nearest second.
For dives with a time based interval, the timestamps are now validated.
