Checkqc

Patch:
Updated Q30 threshold for `hiseqx_v2`.

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

This release changes the behavior when significant unidentified indexes are found from warning to giving an error, i.e. it will make the exit flag of the program `1` instead of `0`.

In addition to this it introduces more sophisticated checks for dual indexes. We will now check each index in a dual index combination separately to see if one of the two e.g. has been reversed, or if the found index matches the complement of an index in the samplesheet.

This release include the following updates:
- The readme now refer to Python 3.6 instead of Python 3.5 since the later version is needed for some modules to run properly.
- Support and QC criteria for NovaSeq SP is now added.
- QC criteria and read length for some instrument types are now in the configuration file.

The documentation regarding iSeq naming conventions was incorrect, the naming convention for iSeqs should be that they start with FS. This is fixed in this version.