[UD] Create backend for dashboard

[JPinkney]

Is your enhancement related to a problem? Please describe.

Currently, with the devworkspace in dashboard work, we're relying on che-servers passthrough to the kubernetes api in order to do things like get all DevWorkspaces, create DevWorkspaces, etc. It would be a great improvement if we can switch to a backend so that the dashboard won't have to depend on so much on che-server. Also, by using a backend we can continue the work on a common library that chectl, che-theia, and dashboard can use

Describe the solution you'd like

Dashboard starts using a backend

Describe alternatives you've considered

Additional context

• WIP Run dashboard as separate deployment
• Provide high-level library for managing DevWorkspace objects for clients
• Begin implementing basic DevWorkspace functionality into new dashboard

[sleshchenko]

now dashboard has different packages for frontend and backend eclipse-che/che-dashboard#268

the only thing left in the current issue scope - adapt syncing to CRW

[sleshchenko]

CRW part if moved to a scope of https://issues.redhat.com/browse/CRW-2009. So closing it now