#10 DataSource doesn't support default case

[Joe Germuska]

Struts permits an application datasource to exist with no defined
"key" or "type" -- there are implicit defaults. However,
StrutsBuilder fails to handle these in two ways, both probably
related to null values for those fields:
the struts-config import can produce a DatasourceConfig with nulls
for those values, but when it's displayed in the GUI, the
Datasource tree node does not indicate that it has children if any
of the children has a null. Also, it is not possible to add a new
DataSource in the GUI without filling in those values. Of course,
users shouldn't have to type in the default values...