Enable WARC file writing and handling in the NetarchiveSuite

NetarchiveSuite should allow the user to store data in either ARC or WARC files.
This means that there also needs to be a setting that says which format is used by NetarchiveSuite.
And that the bitarchives should be able to handle both ARC and WARC files meaning that they should be able to

• store data in both formats
• fetch data in both formats (whole files and per record)
• perform batch-jobs on both ARC and WARC files.