* Refactor common network shared and platform specific code into package (part-1)
As per proposal #76 refactor common network shared and platform specific
code into sub-package.
https://github.com/ansible/proposals/issues/76
* ansible.module_utils.network.common - command shared functions
* ansible.module_utils.network.{{ platform }} - where platform is platform specific shared functions
* Fix review comments
* Fix review comments
* Tidy up docs for network 2.3 modules
* Use suboptions
* Correct indentation
* more tidyup
* bulk updates
* more tidyup
* Bulk changes
* nxos_mtu is dead
* revert
* NXOS_mtu is dead, also better layout
* rebase
* rebase