Fix 'available' flag related NPE in Location.copy()

Avoid auto-unboxing null pointer exception in `Location.copy()` due to
the *available* flag in `Location` being `Boolean` but the `setAvailable`
method parameter being primitive `boolean` for JAXB compatibility.
Merge pull request #110 from atlasapi/fix-location-copy

Fix 'available' flag related NPE in Location.copy()