Do some troubleshooting

remote/add.php:
-cleaned out $addbyurl from add-section (cause we no longer use those in add.php)

remote/inc/defines/torrent.php:
-changed the SIZE_CHUNKS-Value to 19 to fit the d.multicall in details.fun.php on line 390
 --> now the inline-info-tab from a torrent show the right number of chunks

remote/inc/rpc.php:
-show a Error-text when one (or more) rpc-function(s) for rtorrent are missing
 -->"Did you update to new rtorrent/libtorrent version?"