Cleanup dependencies (#201)

* We don't need to shadow in `lombok` itself. Gradle must be upgraded to at least 4.6 to support `annotationProcessor`, which is a version that still supports Java 7.
* `args4j-maven-plugin` is intended to use as a maven plugin.
* The requirement for `jaxb-api` was removed in 81cba7d58c0ce8a334204700dca669f2ad8e16ff
* We are only using `simple-xml`, don't need the whole `retrofit`+`okhttp`+`okio` chain.
* Resolve deprecation warnings in JNA code.

src/com/sheepit/client/hardware/gpu/nvidia/Nvidia.java

@@ -22,7 +22,7 @@ public class Nvidia implements GPULister {
 		}
 		CUDA cudalib = null;
 		try {
-			cudalib = (CUDA) Native.loadLibrary(path, CUDA.class);
+			cudalib = (CUDA) Native.load(path, CUDA.class);
 		}
 		catch (java.lang.UnsatisfiedLinkError e) {
 			return null;

src/com/sheepit/client/hardware/gpu/opencl/OpenCL.java

@@ -40,7 +40,7 @@ public class OpenCL implements GPULister {
 		
 		String path = "OpenCL";
 		try {
-			lib = (OpenCLLib) Native.loadLibrary(path, OpenCLLib.class);
+			lib = (OpenCLLib) Native.load(path, OpenCLLib.class);
 		}
 		catch (java.lang.UnsatisfiedLinkError e) {
 			System.out.println("OpenCL::getGpus failed(A) to load OpenCL lib (path: " + path + ")");