Tell the full report what libraries to get vaf info for

This way they will all have the same columns even if some have no
variants with coverage for a particular library.  This makes the
hacky "split columns" step during the merge unnecessary
This loop will trigger one database query per library if they're not already loaded.  If there are a lot of instrument data, it may be faster/more efficient to do something like:
```perl
my @libraries = Genome::Library->get([map $_->library_id, @instrument_data]);
return map $_->name, @libraries; #already unique after get();
```
It may also be possible to do something like:
```perl
my $instrument_data_set = Genome::InstrumentData->define_set(...);
my $library_set = $instrument_data_set->__related_set__('library');
return map $_->name, $library_set->members;
```
In my (limited) experience, `__related_set__` can't always figure out how to create the new set, though.