UX tweeks to column selector

- use a simple select instead of the blue labels for adding columns
- the "-" needs to be a "circle -": using glyphicon glyphicon-minus-sign
- updated e2e tests accordingly
- rebuilt dist

relates to https://github.com/Rise-Vision/style-guide/pull/36
could @winkerVSbecks and/or @alex-deaconu review & merge?