First release candidate of the 4.3.0 branch.


# Changes
## New features
- Changed internal interacation between the on disk YAML format and the in memory 
  format. This enables the command line options to be autogenerated from the datastructures.
  Also this keeps the options for profiles and node set/add commands in strict sync.
- Added `node edit/export/import` where the edit command exposes the YAML config for the
  given nodes in an editor. Nodes can also be added with this command. The export command 
  simply drops the YAML config for the given nodes. With the import command nodes can be
  imported as YAML or as a CSV file. The CSV file must havr a header in where the first field
  must always be the nodename, the rest of the fields are the same as the long commandline
  options. Network device must have the form net.$NETNAME.$NETOPTION, which would e.g. be 
  net.default.ipaddr
- The default value (like kernel args) are no read in from the configuration file 
  default.conf. If this file couldn't be read built in default values will be used.
- Template files for NetworkManager are now present in the wwinit overlay. A interface must
  have the type ethernet or infiniband that these will be brought up by NetworkManager
- Listings of container via `wwctl container list` will now show the creation,modification 
  date and the size.
- Initial cut of the warewulf API. See https://github.com/hpcng/warewulf/pull/471
## Bug fixes
- For the connections of `wwctl ssh` the primary interface will be used
- Fixed kernel version in `wwctl container show`
- remove the container image and not only the rootfs dir  on delete
- include and exclude handling for container were fixed