Cluster and histogram tools

A pair of tools I have been using for studying resources summaries. One computes clusters according to resources specified (see figure below), and the other computes histograms. E.g.:

find /somedir -name "*.summary" | xargs grep -l -e "^command: SOMECOMMAND" | ./histograms output-dir

Code is a little hackish by iterating structure fields with offsets (see rmon_tools.c), but that allows to add new resources easily, and keeps the computation efficient.

In the example below, with ./cluster we find three clearly different task categories. See that the second column is very similar to the first, only that the task had to swap for some reason (with ./histogram we can easily see which task is the outlier, so these tools complement each other).

![exp4](https://cloud.githubusercontent.com/assets/3081826/2570136/5bfae7c4-b8f5-11e3-9a72-5a5a3fd39ae5.png)