Reorganize code.
Randomly change auto_network/plugin indentation
Move to middleware based implementation
Update documentation for new syntax
Reindent auto_network/pool
Subclass Vagrant error for fancy handling.
Update action/network docs
Store address pool in middleware env hash
Give out pool leases on a per-machine basis

This commit reworks the pool to give out IP addresses on a per-machine
basis. If a machine requests an IP address twice it will retrieve the
same IP address.

This commit also drops the dependency on the `ipaddress` gem.
Handle (de)serialization in action class
Update network action to use new pool
Rearrange middleware stack
Add commenting.
Cleanup logic in action/gen_pool
Remove default initialize param for pool

Setting the default argument is handled by action/gen_pool
Merge branch 'persistent_ip'
Add I18n error message