Add beta/trial GPX -> Nike+ in the (legacy) ConvertServlet.java.
Move from using commons-fileupload 1.2.1 to javax.servlet-api 3.1.0.

javax.servlet-api 3.0+ introduces HttpServletRequest#getParts() for parsing
multipart/form-data data in a servlet.  Switch to using this and remove our
dependency on commons-fileupload.
Improved logging.

Added thread-id to logging output and added some messages around http communication
with garmin and unmarshalling of InputStreams to JAXB objects.
Add reporting plugin findbugs-maven-plugin 3.0.0 to pom.xml