JDownloader

Make sure any data downloaded and progress is preserved on any exception

Currently if long timeouts are present, and download underway from multiple chunks and other chunks fail to connect, all data|progress is lost when exceptions are thrown. This is a waste of data, ontop of that we should look up previous attempt at download progress on download chunks (over 0 bytes|0 percent). Any allocated chunks holding data, should be the next connections upper chunk value, this would effectively prevent infinite loop issue within the current download core and/or incorrect upper limit on chunk value within plugin. We could also then self report this (stat module) of incorrect plugin upper chunk value, so we can adjust default.