Vernalis nodes updated to v 1.8.1

All current versions (nightly, stable 3.1 and 3.2) of our plugins have now been updated to version 1.8.1.

This fixes a bug in the behaviour of the European PubMedCentral Advanced query node following changes to the remote webservice (and adds some additional options to the node configuration)

Additionally further nodes now are 'streamable'.

As always, if any problems, please do let us know.