added setcmd command


git-svn-id: svn://svn.code.sf.net/p/fhem/code@4722 2b470e98-0d58-463d-a4d8-8e2adae1ed80
added docu


git-svn-id: svn://svn.code.sf.net/p/fhem/code@4723 2b470e98-0d58-463d-a4d8-8e2adae1ed80