add context (GA4GH links, team mission)
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 #31 from dglazer/readme-mission

add context (GA4GH links, team mission)
Merge pull request #33 from lh3/master

Structured CIGAR; added barebone GADataSet
Merge branch 'master' of https://github.com/ga4gh/ReadTaskTeam into contribution_documentation