examples+utils: Adding example to evaluate memory footprint of ContentStore/Pit
utils: Removing linux support from mem-usage (needs more careful checking of available headers)

closes #23
model: replacing direct usage of fib::FaceMetric variables by inline methods
model: Finalizing implementation of FaceMetric::Status tracing

Adding test case (ndnSIM-fib-entry), which can be used as an example how
to set up tracing.
utils: Fixing compilation warning
examples: Fixing error in ndn-simple-with-pcap

closes #24
model: Mark face YELLOW when PIT entry times out in ndn::fw::GreenYellowRed strategy
Merge feature branch 'feature-trace-value-for-fib-entry'
helper: New experimental CalculateAllPossibleRoutes method in ndn::GlobalRoutingHelper

Implementation is not time-efficient and it should not be used for very
large topologies.
helper: Fixing unused variable warning
tools: fix compilation warning about an unused return value