warewulf v4 WIP

This is built on CentOS-7. More needs to be done to make it work on other distributions and versions specifically with the system service components.

In a nutshell, to install and start provisioning nodes, do the following:

1. make
2. sudo make install
3. vi /etc/warewulf/warewulf.conf
4. vi /etc/warewulf/nodes.conf
5. sudo singularity build --sandbox /var/chroots/centos-7 centos-7.def
6. sudo ./wwbuild vnfs
7. sudo ./wwbuild kernel
8. sudo ./wwbuild overlay
9. ./warewulfd
10. Boot your compute node