Use the CalculatorEditTextField everywhere.

That way, tablet and phone act the same.
Also, Fixes bug:5215768 IRK56: Selected text in Calculator is left-aligned, but selection handles are right-aligned

By giving the user the same "tap and hold to copy" behavior that tablet has
Which also allows them to put the cursor anywhere in the field and replace/delete

Change-Id: I896934c603833dea45cb7e267471c676fa6238f3