Add the generation of the functions hashCode() and equals() into the events (issue #50).
For solving the issue #50, the generation of the equals() and hashCode() functions must not use the Xtend generators.
Indeed, according to the issues https://bugs.eclipse.org/bugs/show_bug.cgi?id=434912 and
 https://bugs.eclipse.org/bugs/show_bug.cgi?id=392440, these functions are bugged.
We propose a fixed implementation until these bugs are fixed in Xtext.
Fixing the code of the "equal" and "hashCode" function generators (issue #50).
Fixing the document of the join() function (issue #75).