os_region should be made optional in gc3pie.conf

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as it is not trivial to get the 'Region' name for a given Openstack 
installation and considering that 'os_region_name' is not a compulsory option 
to specify, (for the nova client it suffices the os_user_name and 
os_tentant_name), 
I would suggest to make 'os_region_name' optional (if not removing it 
completely!) from the gc3pie.conf and gc3pie.conf.example

S.

Original issue reported on code.google.com by sergio.m...@gmail.com on 7 Apr 2014 at 2:13