Simple rest clent and plugins table.

Plugins table is populated from api.

Change-Id: Ice1c27487a6608476e6987bdfbc9bbbf488e1971
Create nodegroup template flow implementation.

Plugins and hadoop versions are taken from api.
All processes and configurations are stubbed.
Version dropdown is managed by javascript.
Validation fixed.
Minor refactoring.

Change-Id: I9229c567492e1c5362e8c21295ad5fb15fca8533