Add Kernel recipe with microcode installation stanza
user
```ruby
#
# Cookbook Name:: sys
# Recipe:: kernel
#
# Copyright 2017, GSI HPC department
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

# Kernel installation related tasks
#
# - runtime parameters set via sysctl are managed bay the 'control' recipe
# - GRUB related tasks are handled by the 'boot' recipe

if node['sys']['kernel']

  # Detect the CPU vendor
  cpu_vendor = if node['cpu'][0]['vendor_id'] == 'GenuineIntel'
                 'intel'
               elsif false
                 # TODO: detect AMD
                 'amd64'
               end

  # install the CPU microcode updates cf. https://wiki.debian.org/Microcode
  package "#{cpu_vendor}-microcode" do
    only_if { cpu_vendor && node['sys']['kernel']['install_microcode'] }
  end
end
```
assistant