Output file, expected errors in tabbed text format.
Supported by fastq_filter and
fastq_mergepairs. With fastq_filter,
there are two fields: the read label, and the number of expected errors. With
fastq_mergepairs, there are four fields: 1. expected errors in forward read, 2.
expected errors in reverse read, 3. observed errors in forward read, and 4.
observed errors in reverse read. Errors are inferred as mismatches in the
overlap region, the error is assumed to be in the base with the lower Q score.