create single INSTALL.md to consolidate table of content for all installation related docs

We have several ways to install and run openwhisk. I'm enumerating them below.

1. vagrant
1. docker (ubuntu, docker machine, docker for mac)
1. docker composer
1. mesosphere dc/os
1. kubernetes (including minikube)
1. openstack

The install doc should guide interested developers to the appropriate install path by providing an index of the options and possibly a brief guide as to which is suitable for what dev scenario.

The information today is scattered in a number of places:
1. [Gradle](https://github.com/apache/incubator-openwhisk/tree/master/gradle) and [Ansible](https://github.com/apache/incubator-openwhisk/blob/master/ansible/README.md) READMEs
2. mac deployment ([here](https://github.com/apache/incubator-openwhisk/blob/master/tools/macos/README.md) and [here](https://github.com/apache/incubator-openwhisk/blob/master/tools/macos/docker-machine/README.md))
3. docker compose in [dev tools](https://github.com/apache/incubator-openwhisk-devtools/blob/master/docker-compose/README.md)
4. mesos should land [here](https://github.com/apache/incubator-openwhisk-deploy-mesos) but not yet populated (see [for history](https://github.com/apache/incubator-openwhisk-devtools/pull/20))
5. kube and minikube are [here](https://github.com/apache/incubator-openwhisk-deploy-kube/blob/master/README.md)
6. openstack (also used for aws) is [here](https://github.com/apache/incubator-openwhisk/blob/master/ansible/README_DISTRIBUTED.md) and generally not supported/rotting

FYI @akrabat @jthomas @ddragosd @bbrowning