Accept unprefixed message-tags

Closes #13

src/main/kotlin/com/dmdirc/ktirc/events/handlers/CapabilitiesHandler.kt

                 client.sendCapabilityEnd()
             } else {
                 negotiationState = CapabilitiesNegotiationState.AWAITING_ACK
-                advertisedCapabilities.keys.map { it.name }.let {
+                advertisedCapabilities.keys.map { it.names[0] }.let {
                     log.info { "Requesting capabilities: ${it.toList()}" }
                     client.sendCapabilityRequest(it)
                 }
     private fun handleCapabilitiesAcknowledged(client: IrcClient, capabilities: Map<Capability, String>) {
         // TODO: Check if everything we wanted is enabled
         with(client.serverState.capabilities) {
-            log.info { "Acknowledged capabilities: ${capabilities.keys.map { it.name }.toList()}" }
+            log.info { "Acknowledged capabilities: ${capabilities.keys.map { it::class.simpleName }.toList()}" }
             enabledCapabilities.putAll(capabilities)
 
             if (client.serverState.sasl.mechanisms.isNotEmpty()) {

src/main/kotlin/com/dmdirc/ktirc/model/CapabilitiesState.kt

  * IRCv3 capabilities supported by the client.
  */
 @Suppress("unused")
-sealed class Capability(val name: String) {
+sealed class Capability(vararg val names:  String) {
     // Capabilities that introduce extra commands:
     /** Allows authentication using SASL via the AUTHENTICATE command. */
     object SaslAuthentication : Capability("sasl")
 
     // Capabilities that enable more information in message tags:
-    /** Draft version of message tags, enables client-only tags. */
-    object DraftMessageTags33 : Capability("draft/message-tags-0.2") // TODO: Add processor for TAGMSG
+    /** Generic support for message tags, including client-only tags. */
+    object DraftMessageTags33 : Capability("message-tags", "draft/message-tags-0.2") // TODO: Add processor for TAGMSG
 
     /** Messages are tagged with the server time they originated at. */
     object ServerTimeMessageTag : Capability("server-time")
 }
 
 internal val capabilities: Map<String, Capability> by lazy {
-    Capability::class.nestedClasses.map { it.objectInstance as Capability }.associateBy { it.name }
+    Capability::class.nestedClasses
+            .map { it.objectInstance as Capability }
+            .flatMap { it.names.map { name -> name to it }  }
+            .toMap()
 }