Move to FastaTable API, enabling instant start-up times even with giant references

This change has some subtle implications that will have to be
documented in release notes or considered further:

  - We no longer check the MD5s of contigs that we load, and, in
    particular, we no longer do any kind of sanity checking that the
    reference contig that was aligned against is in fact identical to
    the reference contig in the reference FASTA.  I will write a
    separate tool to help troubleshoot this kind of problem, or
    potentially provide a flag for quiver to do it.

  - The behavior for handling disagreement between the set of contigs
    in the reference FASTA vs. in the cmp.h5 is modified.  Formerly,
    we would abort if a cmp.h5 contained a contig not in the reference
    FASTA.  Now, we just WARN in that situation, and proceed to
    process the contigs in both.

  - The reference FASTA must now have a companion .fai file next to it
    in the filesystem.  This is true for all references in the
    reference repository, and outside users can easily do it using
    `samtools faidx`.

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/tools/GenomicConsensus/": change = 128812]
Version 0.8.0

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/tools/GenomicConsensus/": change = 128813]
Add .fai files

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/tools/GenomicConsensus/": change = 128814]
Remove unused test data

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/tools/GenomicConsensus/": change = 128821]
Fix the error handling for mismatched reference and cmp.h5, and add a test

[Tracking bug 23893]

[git-p4: depot-paths = "//depot/software/bioinformatics/tools/GenomicConsensus/": change = 128822]