Redesign pt-diskstats

0. Investigate converting to Perl

This tool can be converted to Perl if Term::ReadKey functionality can be done in pure-Perl for the Linux platform (no need for other platforms) and embedded so no external modules are needed.

1. Use mktemp

Create a temporary directory with mktemp and use this to store the file, instead of hardcoding the file into /tmp. Be sure to remove any temp dirs and files created when the tool exits unless it exits on error, in which case any data it was using in its temp dir might help reproduce the problem.

2. Fix accuracy problems

Fix pt-diskstat bugs for https://launchpad.net/percona-toolkit/+milestone/2.0-beta2

3. Add await and svctm columns

Add columns similar to iostat. Rename them, though: await should be called qtime, and svctm should be called stime. These should appear by default.

4. Hide MB/second, show IOs/second

Hide (by default) the MB written/read per second columns, and show the IOPS/second for reads and writes.

5. Make the tool hide inactive devices.

Devices that are just zeroes should not be displayed (by default). This should be enabled/disabled with the 'i' key to match innotop's keystrokes.

6. Add long-form command-line options

Add proper command-line options that comply with our standards, and include --help, --version, and our other standard options.

7. Add configuration file

This will be done automatically once the tool uses OptionParser and is given a --config option (copy it from another Perl tool).