Enhancement: enable bulk addition of files to collection

[schorlton]

Currently, if files are to be added to a collection, the plus icon has to be clicked for each file. There should be a bulk selector and select all button to enable rapid addition of large numbers of files to collections.

[TKlingstrom]

We have noted the improvement and agree but we are short on programming capacity. We appreciate all help we can get on improving/updating Galaksio and otherwise I think any major work will have to wait until the autumn.