SEC-1689: Re-instate crypto as separate library (for use in non-Spring Security apps), as well as packaging with core.

crypto/crypto.gradle

@@ -0,0 +1,12 @@
+// crypto module build file
+
+// jdkVersion = System.properties['java.version']
+// isJdk6 = jdkVersion >= '1.6'
+int maxAESKeySize = javax.crypto.Cipher.getMaxAllowedKeyLength('AES')
+
+test {
+    if (maxAESKeySize < 256) {
+        println "AES keysize limited to $maxAESKeySize, skipping EncryptorsTests"
+        exclude '**/EncryptorsTests.class'
+    }
+}