- show correct domain type as field type name
- correctly determine length and precision of domain types
- expose bpchar field type as 'character' to users, as postgres only
uses 'bpchar' internally and refers to bpchar as character in the
front end
- make QgsVectorFileWriter respect QTime field values and only
convert to string if required by output format
- list time types as native types for memory, postgres and OGR
providers (OGR support depends on file format)