perf c2c report: Add 'node' sort key

It is to be displayed in the single cacheline output:

  node

It displays nodes hits related to cacheline accesses.

The node filed comes in 3 flavors:
  - node IDs separated by ','
  - node IDs with stats for each ID, in following format:
      Node{cpus %hitms %stores}
  - node IDs with list of affected CPUs in following format:
      Node{cpu list}

User can switch the flavor with -N option (-NN,-NNN).
It will be available in TUI to switch this with 'n' key.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Joe Mario <jmario@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-6742e6g0r7n63y5wc4rrgxx5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>