Support Tomcat uri encoding (with UTF-8 default)

Introduce an extra `server.tomcat.uri-encoding` property used to
configure the URI encoding for the embedded tomcat container.

Defaults to `UTF-8` instead of the usual tomcat default of `ISO-8859-1`.

Fixes gh-540
Merge pull request #542 from snicoll/gh-540

* gh-540:
  Support Tomcat uri encoding (with UTF-8 default)