Fill in the subsection "Requirements and constraints to parallelize EAs on GPUs"

[amorag]

And choose a better title... :D

The idea here is to describe overall the way to parallelize EAs on GPUs: requirements, issues to consider, constraints that GPUs have (to do this task), etc

Try to avoid overlapping with the taxonomy section. ;)

[amorag]

This is Section 5. Update and improve 5.1 and complete 5.2.