Huge viewport update for next version + issues fixes

1. Added sorting none
2. Initially revo-grid had structure as:

<revo-grid>
  <viewport/>
  <some extra elements/>
</revo-grid>

The viewport was an additional layer of complexity. Initially introduced as a proxy.
We are removing this layer to simplify things and bring direct order of store load and communication with internal components.

3. #188 fix