Add source "data based solely on DAISIE portal" to distribution

[peterdesmet]

For records with the note:

data based solely on DAISIE portal

Add that exact phrasing as source in the distribution extension. It will allow to differentiate between distributions for the same taxon or to exclude those for the unified checklist. Even though it is not the best way to write a source (i.e. not a proper citation), it is referenced as such in the paper (search on "solely") and thus more easily findable. Alternatively, we could use the proper citation:

DAISIE European Invasive Alien Species Gateway (http://www.europe-aliens.org/)

But that doesn't clarify that that it was solely based on those or use the field occurrenceRemarks, but is seems to fit better with source. @qgroom preferences?

[LienReyserhove]

if we use option 2, I would clearly indicate in the metadata that in this case, the ONLY source was DAISIE.
Nevertheless, I'm a fan of the first option as this is how we received the data