OpenShift API implementation

[gorkem]

Implement DockerConnector APIs using OpenShift counterparts.

[ ] Images
- buildImage
- commit
- inspectImage
- listImages
- pull
- push
- removeImage
- tag
[ ] Network
- connectContainerToNetwork
- createNetwork
- disconnectContainerFromNetwork
- inspectNetwork
- removeNetwork
[ ] Exec
- attachContainer
- createExec
- startExec
[ ] Info
- getContainerLogs
- getEvents
- getExecInfo
- getNetworks
- getNetworks
- getSystemInfo
- getVersion
- top
[ ] Containers
- listContainers
- getResource
- putResource
- removeContainer
- startContainer
- stopContainer
- waitContainer

[l0rd]

This tasks are needed to remove --privileged container constraint for running Che workspaces in OpenShift (third bullet of #2847).

Other tasks are:

• remove usage of hostPath volumes for workpaces (a solution is to download agents via http and [WIP] Hackathon merge #3013 should implement it)
• allow to run workspaces behind a reverse proxy (cf PR [WIP] Replace client side HTTP requests using the hostname that is in the address bar #2004)

[ibuziuk]

I am going to work on Containers implementation, @amisevsk on Network & Exec and @snjeza on Images

[TylerJewell]

Superceded by epic tracking all activities.