tests.detector: abstract NDS host
tests.detector: added Channel.query_nds2 test
utils.lal: fixed weird import bug
StateVector: use Flag.known instead of Flag.valid
DataQualityDict.write: added unified IO write
DataQualityFlag: added deleters for segment lists
DataQualityFlag.known: do not set known via active

    - if user doesn't give known, that's fine, just leave it
DataQualityFlag.regular: new property

    flag.regular tests whether active is a proper subset of known
DataQualityFlag.coalesce: now makes flag regular
segments.flag: improvement docstrings

    - sphinx should automatically know about the classes, so we dont
      need to give the directives, or the modules
DataQualityDict.read ligolw: don't coalesce by default
segments.io.segwizard: two changes

    - reading from segwizard now sets known == active
    - writing DataQualityFlag to segwizard will fail if information will
      be lost by writing only the active segments
tests.segments: added segments testing

    - not finished yet, needs DataQualityDict tests, but all current
      tests pass