Add encrypt/decrypt commands (use -k to specify key)

The key format can be plaintext (symmetric key, not recommended but quick
and dirty), or PEM encoded key data, or (for encryption only) a base64
encoded public key (like in ~/.ssh/id_rsa or like you get from the
Spring Cloud configserver /key endpoint).

spring-cloud-cli/pom.xml

@@ -38,15 +38,14 @@
 	</dependencyManagement>
 
 	<dependencies>
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-rsa</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-cli</artifactId>
             <version>${spring-boot.version}</version>
-            <scope>provided</scope>
-		</dependency>
-		<dependency>
-			<groupId>org.springframework.cloud</groupId>
-			<artifactId>spring-cloud-netflix-eureka-server</artifactId>
             <scope>provided</scope>
 		</dependency>
 		<dependency>