iotop 0.6 + linux user config file

xtraeme:
I don't know if you wanna accept my pull request, but I decided to separate distro config file, if the user has his own configs.
Why? I find it interesting to have a "hard-coded" config by you and if the user decides to create his own file <code>${arch}-dotconfig-custom</code>, he won't modify the default config included.
We can compare both version, and this file <code>${arch}-dotconfig-custom</code> won't be upgraded.
I think it's better.