small change in error message text

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1181 b1b436ca-2b18-4f33-ab5d-510789358d54
improved news server connections handling: if a download of an article fails due to connection error the news server becomes temporary disabled (blocked) for several seconds (defined by option "RetryInterval"); the download is then retried on another news server (of the same level) if available; if no other news servers (of the same level) exist the program will retry the same news server after its block interval expires; this increases failure tolerance when multiple news servers are used

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1182 b1b436ca-2b18-4f33-ab5d-510789358d54
added support for negative numeric values in rss filter (useful for fields "dupescore" and "priority")

git-svn-id: svn://svn.code.sf.net/p/nzbget/code/trunk@1183 b1b436ca-2b18-4f33-ab5d-510789358d54