split vidtrans.c into smaller files
document more code

restructure the internal logic of file transfers, that is:
- build a list of cvideosources for every minute in a recording + overhead of 10..50%
- try to match these snippets so that they merge to one recording, without double data and without gaps
- then hand each snippet to a clientthread (telling him where to start writing and how much to write)
- execute and mark each snippet as done when the client returns with success

in the meantime: 
- per minute one clientthread will start, each transfer will gather 66s instead of 60s
- then parsefile has to run over the many snippets
- and a cutter has to try to match the pieces together

verify that the rescheduling of blocks and renaming of available blocks do the right thing

test transfers through the network (not just from localhost)

implement correct what-to-do-if processsnippetlist finds snippets that have state "dirty"; so far it is indistinguishible for vdrrecordings if that snippet is still downloaded (leave it as it is) or if the download is broken (either delete it or reschedule it with offset = filesize)
	this could perhaps be achieved by passing information about clientthread _threadnumber's state to vdrrecordings. But is this really wanted? Even more state...

implement resume-at-offset-x for ctasks/task/clientthread --> vdrrecordings::reschedule


