Revising styles for PB Data Criteria Dialog

- Working on getting things to align better and for the forms to not
  change size.
DC form has corrected format & style

- Form elements are correctly spaced out
- Checkbox uses the same icons as everywhere else
- Moved checkbox styles to mixins.less
- .checkbox-population is now .checkbox-label to be more generic and
  semantic since it is now used across the application
Trying to fix PUT error on PB