Chimeric view menu item disabled for linked alignments

[jrobinso]

The chimeric menu item is disabled for linked alignments (class LinkedAlignment). This is because the SA tag is null. Arguably this should work, perhaps by grabbing a representative SA tag from one of the constitutive alignments.

For testing, attached session opens with a few linked alignments, in the top "SUPPLEMENTARY" group. The linked alignment with components colored by strand is good for testing as it contains mixed strands.

schatz_skbr3_pacbio_sampled.xml.zip