[#1963] Loop through all values in error dict on datapusher wui page

Adds extra info to the datapusher/datastore upload log page on the web
interface.

The datapusher actions return ValidationErrors whose dicts can contain
various keys, e.g

ValidationError({
    'constraints': ...
    'info': {
        'orig': ...,
        'pgcode': ...,
    }
})

or

ValidationError({
    'data': ...,
    'info': {
        'orig': ...
    }
})

Instead of displaying just error.data, iterate through the error dict.