Fastq-filter

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+ Improved performance by:

+ Slight rewrites in the multiple FASTQ pipeline. Cases with one, two, three
and multiple FASTQ files are now handled separately. This vastly improves
the speed of especially the single and paired end instances.
+ Rewriting the filters in C.
+ Added logging with basic stats. When ``--verbose`` is set, the counts for
individual filters are reported. With ``--quiet`` logging can be turned off.

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+ Add ability for filtering paired sequences.
+ The minimum dnaio version requirement was bumped to 0.9.0.
+ Drop Python 3.6 support as Python 3.6 is end of life.
+ Filters are now applied by command flags. This is easier to understand than
the previous method (which selected methods using strings). It is also
easier to program and document.

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+ Various documentation fixes
+ Include a galaxy wrapper

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+ Use a lookup table for faster quality lookup
+ Add checking to ensure all quality values are correct.
+ Create a fastq-filter program with functions for length, mean quality and
median quality filtering.