Add tags to allow more granular tasks filtering.
Add generator script for MD formatted tags found.
Add docs for tags how-to.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

Squashed commits:
[f9355ea1] Swap order in which we reload docker/socket
[2ca6819c] Reload docker.socket after installing flannel on coreos

Workaround for #569
[9f976e56] Vagrantfile: setup proxy inside virtual machines

In corporate networks, it is good to pre-configure proxy variables.
[9d7142f4] Vagrantfile: use Ubuntu 16.04 LTS

Use recent supported version of Ubuntu for local development setup
with Vagrant.
[50f77cca] Add CI test layouts

* Drop Wily from test matrix
* Replace the Wily cases dropped with extra cases to test separate
  roles deployment

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>
[03e162b3] Update OWNERS
[c7b00cae] Use tar+register instead of copy/slurp for distributing tokens and certs

Related bug: https://github.com/ansible/ansible/issues/15405

Uses tar and register because synchronize module cannot sudo on the
remote side correctly and copy is too slow.

This patch dramatically cuts down the number of tasks to process
for cert synchronization.
[2778ac61] Add new var skip_dnsmasq_k8s

If skip_dnsmasq is set, it will still not set up dnsmasq
k8s pod. This enables independent setup of resolvconf section
before kubelet is up.

Workaround for #569

* Add the retry_stagger var to tweak push and retry time strategies.
* Add large deployments related docs.

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

Creating the unit using default settings early on
and then changing it during network_plugin section
leads to too many docker restarts and duplicated code.

Reversed Wants= dependence on docker.service so it does not
restart docker when reloading systemd

Consolidated all docker restart handlers.

Default version is still unchanged, but added docker versions 1.11 and 1.12

Changed Wants=docker.service to docker.socket

Renamed handlers for reloading systemd to contain role in task name.

This allows Ubuntu/Debian to downgrade Docker version if
a newer version is installed, instead of failing.

On CoreOS where there is no package management, perform zero-trip
loops instead of throwing an exception for iterating over a member
of an undefined variable.

 Please enter the commit message for your changes. Lines starting

variables.

1. AWS has issues with ext4 (use xfs instead for CentOS only)
2. Make sure all the centos config files are include in the systemd config
3. Make sure that network options are set in the correct file by os family

This allows downstream items like opencontrail and others change variables
in expected locations.

install docker on a largest number of linux distribution (based on https://github.com/marklee77/ansible-role-docker)