Implement generator function

[ZainlessBrombie]

Generators can be used in the @string annotation: {generated firstnameF}
-> let users register their own generators
-> provide set of default generators
-> let users access the generators manually
Set of default generators right now:
firstname - a random first name from a set of fe/male names
firstnameF - a random name from a set of female first names
firstnameM - a random name from a set of male first names
lastname - a random name from a set of last names
username
password
street
city