intermediate upload feature to check for merges

[ChristianBeer]

Add some way to do an intermediate upload to factordb to check if there was a merge. Could be automatic or semi-automatic:

• Option to upload every X iterations and download elf again. Problem here is that aliqueit currently has no download capability which might get complicated since a lot of errors can happen there.
• Option to stop sequence after X iterations or X iterations after a downdriver that lasted for at least Y iterations or after the sequence dropped below size X and came up again.

Especially the last case would save a lot of computations when a sequence drops below a size of 20 and merges with another sequence that goes up to 160 again. Since aliqueit is running offline and can't detect the merge it has to upload the intermediate result to FDB.