Added site in Slab RSpec format, for easier filtering

Added site in Slab RSpec format, for easier filtering
on the nodes.
	+ Added SlabLocation class in slabv1Node
	+ Changed connecton information which is based on
the location of the node. If nodes from multiples sites are selected, the user
is told how to connect via ssh on each site in the network item, with the "ssh"
attribute list.
Added a check upon lease creation, so that the lease duration
is compliant with Senslab's minimun experiment duration.