Update BGC classes

[gcroci2]

In nplinker, we added support for MIBiG v4.0 (#286), which uses a new schema for its metadata. Biosynthetic classes have changed in v4.0, and this is the mapping between the old and new classes (see also here):

• NRP -> NRPS
• Polyketide -> PKS
• RiPP -> Ribosomal
• Terpene -> Terpene
• Saccharide -> Saccharide
• Alkaloid -> Other

We need to add support to the new classes in the webapp. We could use npl.config.mibig.version to dynamically decide what BGC classes to use.