Extended CIGAR; added barebone GADataSet

It is now possible to describe the entire chimeric alignment in one GARead
record. In case of a graph reference, each linear alignment could be an
alignment to a segment in the graph.
change cigar operation to long names
renamed CIGAR operations
Merge pull request #33 from lh3/master

Structured CIGAR; added barebone GADataSet
Merge remote-tracking branch 'upstream/master' into sets--to-groups

Conflicts:
	src/main/resources/avro/ga4gh.avdl