Tidy up formatting (whitespace) on NikePlus.java
Add maven-jaxb2-plugin to pom.xml and added Garmin's TrainingCenterDatabasev2.xsd to src/main/resources

We can now generate java sources from the Garmin's TrainingCenterDatabasev2.xsd using the "mvn generate-sources" target.
Converted TrainingCenterDatabasev2.xsd line-endings from CR+LF to LF
Add "project.build.sourceEncoding" (UTF-8) to pom.xml properties
Specify versions for maven-compiler-plugin and maven-jaxb2-plugin in pom.xml
Add xsd files for unmarshalling garmin GPX (gpx.xsd, GpxExtensionsv3.xsd and TrackPointExtensionv1.xsd)
Modify NikePlus.java to always use CloseableHttpResponse objects and always call EntityUtils.consume(httpEntity);
Add new methods to Garmin.java which will use JAXB unmarshallers on responses from Garmin http requests, returning java representations