Restore ability to set custom kernel and cmdopts

In the Grizzly we provided an option in site.pp to allow users
to specify that a custom kernel should be loaded on their nodes
and booted by default.  We also provided an option to specify
custom command line options to be fed to the kernel.  When we moved
to the new data model, those options were (temporarily) lost.  This
commit restores them by providing a hiera lookup and corresponding
actions affeting the preseed file.

Partial-Bug: #1263310
Merge pull request #34 from CiscoSystems/bugs/1263310_kernelstuff

Restore ability to set custom kernel and cmdopts
Add ability to set time zone

In Grizzly releases we had an option in site.pp to allow users
to specify the time zone they were in.  This commit adds
a hiera lookup for the time_zone option and passes it on to
the cobbler manifests accordingly.

Partial-Bug: #1263310
Merge branch 'bugs/1263310_timezone' of https://github.com/CiscoSystems/puppet-coi into bugs/1263310_timezone

Conflicts:
	manifests/profiles/cobbler_server.pp