K8s/OS infrastructure should use PVCs as Che Volumes

[sleshchenko]

Description

The idea is to make it possible to use base K8s/OS recipe content for workspaces. It comes from Devfile workflow.
Now a user is forced to declare machines and Che Volumes inside them to have an ability store data.
K8s/OS infrastructures should support PVCs in recipes and resolve them as Che Volumes.
The difficulty of implementing comes from PVCs strategies:

• in the unique strategy, original user-defined PVC may be created;
• in common and perWorkspace strategies, it is needed to convert all user-defined PVCs into one PVC (subpaths may be used to separate one PVC files from another);