Enhance stop order form with new position linkage and slider functions

[JonRay15]

The Chore

It isnt there currently and it should be ... same as limit / market order

Acceptance Criteria

• [x] Add a new pair of radio buttons to set Amount vs Percentage of position under the Size input
• [x] If Amount is selected behave as usual
• [x] If percentage of position is selected display a size slider where the max is 100%
• [x] Apply this to both the Stop Limit and Stop Market form

Additional details / background info

Radio button style