Check the same hashkey we're looking up.

Avoid regenerating the list every time!
FL: Have `merge` wrap `import` instead of `create`.

Thus we run the reference validation logic when combining lists, too.
Validate the properties early on.
Typo: convertion => conversion.
Accessors for other references via converters.
Verify the supplied MD5 against the supplied BED.

It should determine the MD5 "automatically". As long as it's being
supplied separately, make sure our result isn't a total lie!
Support merging lists with different references if we can.
Spelling: cordinates => coordinates.
Remove strange phrase about coordinates for annotation.
Include the BED file in the error message.
Use existing is_derived_from implementation.
Quiet warning when reference has no coordinates_from.
More thorough compatibility check.

* Both the chromosome names must match and the metadata must indicate
that they're "the same" and not coincidentally named the same way.
Extract combined reference search into refseq builds themselves.
Extract validation into a subroutine.
Extract "contains" subroutine into reference sequence itself.
Use for loop to avoid block inside of hashref constructor.
Less accuracy since LIMS uses ancient Perl.
Merge pull request #261 from tmooney/fl_merge_refseq_handling

Improved Feature-List Merge Support