Don't break with strange INFO or FILTER (or other) headers

At the end of the snpEffBuildAndRun process we check that there are not too many warnings in the VCF output. This uses PyVCF. Unfortunately PyVCF isn't able to parse some headers, in this case some INFO and FILTER headers. These aren't what we're looking to check so I've updated the script to ignore them entirely.

A future version of PyVCF might be able to parse these headers better, in which case these commits could be reverted, but this seems like a pragmatic solution for now.