Makeconf

This is a long one, so it might need some looking over.

Gentoo maintains a file, make.conf to set various global emerge related settings. This module allows for adjusting the variables in this file. It has several functions for altering common variables in make.conf, but does maintain functions for every variable (there can be many variables in the file). It also has some generic functions for modifying an arbitrary variable in make.conf. This allows for modifying the more rare variables by passing the variable along with the desired value. 

If this looks good enough to get merged, I will start crafting a state for the make.conf that uses this module.