Previously, only folders on the classpath would be watched and used
to trigger a restart/reload of the application. This commit adds a
new property spring.devtools.restart.additional-paths that can be
used to configure additional paths that should be watched for
changes. When a change occurs in one of those paths a restart or
reload will be triggered, depending on the full restart exclude
patterns configured via the existing spring.devtools.restart.exclude
property.

Closes gh-3469