Base with proxy and save shouldn't be part of classes hierarchy

[andreybs11]

We are aware of known issues happening because the proxy and save were attached as part of components classes hierarchy (from BaseComponent) instead of using composition

Known issues

• Landing components can't detect emptiness state
• Proxy or save can't be added to any level of the components tree, so they were always required at root component of view

Suggested solution:
Create the concept of flows which are managed by handlers. This will let us separate proxy (will be known as 'fetch-flow') and save-flow to be compose into any component class definition