fixes RM7676 migrate -h doesn't produce help

also adds YARD doc to cmd_migrate in collusion with egypt.
low threat change, but still tested on Win7-32 sp0, ruby 1.9.3-p125,
Framework Version: 4.6.0-dev just for kicks

Author: kernelsmith

lib/rex/post/meterpreter/ui/console/command_dispatcher/core.rb

@@ -329,8 +329,11 @@ def cmd_migrate_help
 	#
 	# Migrates the server to the supplied process identifier.
 	#
+	# @param args [Array<String>] Commandline arguments, only -h or a pid
+	# @return [void]
+
 	def cmd_migrate(*args)
-		if (args.length == 0)
+		if ( args.length == 0 or args.include?("-h") )
 			cmd_migrate_help
 			return true
 		end