Better build hist wrapping

2 commits that try make text wrapping in the build history widget a bit nicer:

1. Change the dates to just the time of day and then introduce date separators in the history, so builds from a given day are grouped together. (related to [JENKINS-25381](https://issues.jenkins-ci.org/browse/JENKINS-25381) )
1. Introduce zero-width spaces in long words in the build name and description, allowing them to wrap more cleanly.

![screenshot 2014-11-19 13 49 31](https://cloud.githubusercontent.com/assets/429311/5088294/d32da238-6f29-11e4-9bb0-dbf1447b7404.png)