[web] allow configuration of the Content-disposition value
The `set_content_type` function now takes and optional `disposition` parameter
to control the value of this HTTP header.
Use of `Content-disposition: inline` with a filename parameter are valid, so
the presence of filename does not allows to choose between `attachment` and
`inline`
# migrate default format for TriInfo `comment_format` attribute
sync_schema_props_perms('TrInfo')
commit()