BF: Cherrypick changes from dev to fix pavlovia syncing

[TEParsons]

Changes:

• Access Pavlovia projects via namespace/name string rather than numeric ID, unless numeric ID is all we have
• Don't request info from Pavlovia if we have it locally
• Handle genuine project not found errors (i.e. where the project has actually been deleted) via dedicated dialog rather than unhandled error
• Handle avatar too big with dedicated dialog rather than unhandled error

[TEParsons]

There's a few commits from dev squashed in to one here, but I believe Git should handle that and recognise that the changes are identical when we merge release into dev? If not I can handle merge conflicts