integration of plotToPng() function and small adaptions to RSS for ease of use in RSS feeds

git-svn-id: https://svn.code.sf.net/p/fhem/code/trunk@4147 2b470e98-0d58-463d-a4d8-8e2adae1ed80
YAMAHA_AVR: fix missing greater-than sign. Use different Control-Tag name for RX-Vx75 series

git-svn-id: https://svn.code.sf.net/p/fhem/code/trunk@4148 2b470e98-0d58-463d-a4d8-8e2adae1ed80
YAMAHA_AVR: new attribute request-timeout.

git-svn-id: https://svn.code.sf.net/p/fhem/code/trunk@4149 2b470e98-0d58-463d-a4d8-8e2adae1ed80