[x] create new service preprocessing and inject it into SidebarCtrl
[x] service should provide method scale that implements feature standardization
[ ] add scale method to [prepareData](https://github.com/SOCR/SOCRAT/blob/dev/app/scripts/analysis/tools/Cluster/ClusterSidebarCtrl.ctrl.coffee#L129) method after filtering out chosen features
[ ] display switch in the sidebar allowing user to turn off standardization (should be ON by default), don't forget to add the label
Feature scaling is important pre-processing step for distance-based ML methods
preprocessing
and inject it intoSidebarCtrl
scale
that implements feature standardization[prepareData](https://github.com/SOCR/SOCRAT/blob/dev/app/scripts/analysis/tools/Cluster/ClusterSidebarCtrl.ctrl.coffee#L129)
method after filtering out chosen features