Less stringent alignment and seed filtering

[hmusta]

• No default limit on the total number of output alignments
• If a seed has a filtered-out label, report the seed as an alignment without extending it
• Annotate dummy node seeds with labels of their nearest annotated nodes
• Introduce alignment chaining from MetaGraph-MLA

TODO

• Merge reported seeds into MEMs (since it outputs too much)
• When merging seeds with coordinates, ensure that the coordinates are consistent
• Figure out why some extensions are not happening
• Alignment is too slow and timing out, figure out why
• Chain together filtered-out seeds to cheaply get longer alignments