Abuse Reports message truncation

## What does this MR do?

Adds dynamic message truncation to abuse reports

## Are there points in the code the reviewer needs to double check?

Is the new UI OK?

## Why was this MR needed?

Admin UX

## What are the relevant issue numbers?

Closes #13664.

## Screenshots (if relevant)

**UPDATED:**

![Screen_Shot_2016-07-07_at_03.02.43](/uploads/2e1a1122e0194f8ffa48054c18523ccd/Screen_Shot_2016-07-07_at_03.02.43.png)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
Closes #13664

See merge request !5032