[BUGFIX] Make file uploads work again
This change fixes a regression which was introduced by
Ib5acdb59ee2ff9593456fe35960cdc9c41d71ace. That change
created a second TypeConverter for Resource objects, but
gave a wrong priority for that one -- effectively disabling
the default type converter which handled file uploads.
Here, we merge the behavior of both TypeConverters into
a single one.
When testing this, make sure to fully clear your cache.
Releases: master, 2.2