Traces: Migrate pagination to bootstrap

Same feature, different style.
- Change pagination to use bootstrap default styles
- … but with empty span-tags instead of non-active a-tags
- refactor partial to not use @-variables but get the variables via
the render-call, simplify render-call-syntax
- remove the additional `if @traces.size > 1` inside the pagination
partial since that caused the pagination to disappear on the last page.
The partial will be visible with inactive links.
- Add bootstrap spacer-classes to overwrite commons-css so removing. Eg.
commons also has a pagination class same as bootstrap.