Checkqc

Patch release:
- Fixed problem where NovaSeq SP couldn't be run 88

It is possible to instruct CheckQC to use the closest read length if the read length of the run is not found in the config. In case of a tie between two read lengths, the longer read length (with stricter QC criteria) will be used.

Usage:
` $ checkqc --use-closest-read-length <RUNFOLDER>`

This parameter can be supplied to the webservice as a query argument:
`curl -s -w'\n' localhost:9999/qc/170726_D00118_0303_BCB1TVANXX?useClosestReadLength | python -m json.tool`

It is now possible to downgrade errors to warnings for specific handlers. Prior to evaluating the QC criteria, the config will be updated so that `warning threshold = error threshold` and `error threshold = unknown`. Read more about usage in the docs.

It is now possible to specify white-list indexes that only cause warnings even if they occur above the significance level.

Patch:
Updated Q30 threshold for `hiseqx_v2`.

Patch:
QC criteria for NovaSeq SP, read length 101 bp, have been added to the default config.