Handle searching for matching elements in an array

Add unit tests.
Refactor internals to allow reusing assertion method for finding matches in an array.

ebean-test/src/test/resources/contains/array-multi-match.json

@@ -0,0 +1,20 @@
+[
+  {
+    "a": 1
+  },
+  {
+    "b": 2
+  },
+  {
+    "c": 3
+  },
+  {
+    "d": 4
+  },
+  {
+    "e": 5
+  },
+  {
+    "f": 6
+  }
+]