Sysctl definition

Moved all sysctl related changes to a definition.

Creating a separate file for our own sysctl configuration.

Link that file into /etc/sysctl.d which is loaded at system startup.

Allows editing sysctl values and it reloads the configuration after editing.

Confirmed working on CentOS release 6.5 (Final).

Fixes #662 (closed)

Fixes #700 (closed)

Hopefully fixes #788 (closed)