Add option to include stack traces in syslog

Syslog doesn't work well with stack trace data. The Logback
`SyslogAppender` provides an option to exclude this data, logging only
the name of the Throwable and its message.

We should provide this option to users.
Merge branch 'master' into feature/syslog-exclude-stacktraces
Merge pull request #393 from nicktelford/feature/syslog-exclude-stacktraces

Add option to include/exclude stack traces from syslog
Make ResourceTest a JUnit TestRule

TestRules are much more flexible. They can be run at either the class or
the test level, and can be combined with other TestRules for more
complex behaviour.
Merge pull request #394 from nicktelford/feature/resource-test-rule

Make ResourceTest a JUnit TestRule
Remove logging of dispatch time in request log

The call was deprecated in Jetty 9 and is now a no-op, so removing it
has no impact.