Content Store tracer graphing, updates on rest

The new cs-tr-j.R takes care of graphing the Content Store hit rates for NDN
simulations.

l2-tr-j.R has been modified use subset instead of the array notation.

nms-disaster-ccn_zl.cc was modified to test out the content store trace. At
the moment it asks for two interests, at two different time intervals. This
is a slightly different scenario.

Will have to speak to the team about how to populate the content stores
randomly.

Cheers.