Change charsetName to "UTF-8" when replacing line breaks.

Change charsetName to "UTF-8" when replacing line breaks.

JavaScript requires the charsetName to be "UTF-8". CharsetName values
that work in Java (such as "UTF8") will not work when compiled to
JavaScript.

This fixes a problem with multi-line details view fields that have hard
line breaks. The "License Text" field on this page demonstrates the
problem:

http://onlineglom.openismus.com/OnlineGlom/#details:document=debian_repository_analyzer&table=licenses&value=197

* src/main/java/org/glom/web/client/ui/details/DetailsCell.java: