Fixes for unsightly underlined leading/trailing whitespace in hyperlink text

Sorry if this is the most trivial pull request you ever receive, but this is something that bugs me every time I look at Jenkins.

This is ugly:

![screen shot 2013-08-27 at 01 01 17](https://f.cloud.github.com/assets/147396/1030140/3adaa4ec-0eac-11e3-9452-ac24e5361898.png)

This is better:

![screen shot 2013-08-27 at 01 01 25](https://f.cloud.github.com/assets/147396/1030139/3a3e8b8e-0eac-11e3-861b-b5089f528c65.png)

In addition to the pictured change, there were also underlined trailing spaces on the job names on the main screen. I've tried to make sense of Jelly's whitespace/new line handling rules and I tried using the `trim=true` attribute but in the end the only thing that worked for me was to eliminate the new line before the closing tag in `core/src/main/resources/lib/layout/breakable.jelly`. Maybe somebody who knows more about Jelly could suggest a better fix, but this works OK for now.