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Shorten line length of issues and mrs

Limits container width on issue and mr pages. Shortens line length to human readable length.

![Screen_Shot_2016-12-02_at_12.48.08_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/740647c0fd6ea4f0f0aef62155992afe/Screen_Shot_2016-12-05_at_12.54.12_PM.png)

Closes #20916 
Closes #24408

See merge request !7858