New hash signature property for class individual.

Closes issue 1
Fixed test2 compilation error.
Fixed example3 compilation error.
CSV support for datasets.
SR: source code clean-up.
Various improvements to doxygen documentation.
Updated random class documentation.
Other improvements to random class.
Improved test framework.
Small improvements to analyzer class.
Small corrections to remarks.
More corrections...
Symbol_set now stores symbols also by type.

Update issue 5
Status: Started
This is only the first step. The remaining part of this issue (individual
generation / recombination) hasn't been handled yet.
Initial support for XRFF file format.

Update issue 6
Added support for CSV-Google-Prediction

Update issue 6
New utility for CSV to XRFF conversion.

Update issue 6
More resilience reading malformed XRFF dataset.
Better management of symbol categories (mainly in data class).

Update issue 5
Update issue 6
Improved checking for individual class.
Fixed problem with the signature of the individual returned from get_block method.