Enhancement - Use same example in 'Tutorial Cluster' and 'Distributed-Sharding'

[santo-it]

sharding http://orientdb.com/docs/master/Distributed-Sharding.html and cluster http://orientdb.com/docs/master/Tutorial-Clusters.html

they contain two examples:

in one, class = Customer and clusters = USA_customers and China_customers

in the other, class = Client and clusters = client_usa, client_europe, client_china

to improve experience of new users (that try to understand these concepts for the first time) it would be good/useful to use the same example here (eg, as often these two pages are read at the same time)

will be useful also when creating slides on these concepts