Use the BouncyCastle provider so we can be sure we won't get

NoSuchAlgorithmExceptions. Key generation is *slow* - I guess that's a
good sign. ;-)

api/net/sf/briar/api/crypto/CryptoComponent.java

@@ -0,0 +1,17 @@
+package net.sf.briar.api.crypto;
+
+import java.security.KeyPair;
+import java.security.MessageDigest;
+import java.security.Signature;
+
+
+public interface CryptoComponent {
+
+	KeyPair generateKeyPair();
+
+	KeyParser getKeyParser();
+
+	MessageDigest getMessageDigest();
+
+	Signature getSignature();
+}