Add NativeProblem that loads libeva2problem.jnilib if present.

closes #47

resources/NativeInterface/eva2problem.c

@@ -0,0 +1,29 @@
+#include "eva2_problems_NativeProblem.h"
+
+JNIEXPORT jdoubleArray JNICALL Java_eva2_problems_NativeProblem_evaluate
+  (JNIEnv *env, jobject obj, jdoubleArray array) {
+  int i;
+  double result[1] = {0.0};
+  jdoubleArray resultArray = (*env)->NewDoubleArray(env, 1);
+  if (resultArray == NULL) {
+    return NULL; /* out of memory :( */
+  }
+  jsize len = (*env)->GetArrayLength(env, array);
+  jdouble *body = (*env)->GetDoubleArrayElements(env, array, 0);
+
+  // Calculate sum(x_i^2)
+  for(i=0; i<len; i++) {
+    result[0] += body[i] * body[i];
+  }
+
+  // Release input array
+  (*env)->ReleaseDoubleArrayElements(env, array, body, 0);
+  // Set result
+  (*env)->SetDoubleArrayRegion(env, resultArray, 0, 1, result);
+  return resultArray;
+}
+
+JNIEXPORT jstring JNICALL Java_eva2_problems_NativeProblem_getName
+  (JNIEnv *env, jobject obj) {
+  return (*env)->NewStringUTF(env, "Native Sphere");
+}