new gda component

[Rodrigo Moya <rodrigo linuxave net>]

Hi all!

I've thought of another config component we can have. If you use
unixODBC (http://www.unixodbc.org), you'll see that, in the Driver
Manager (where you configure the data sources), you are first prompted
for a driver, and then, it loads a list of property names from the
chosen driver. This list defines all the parameters the driver needs to
configure a data source.

So, a gda-postgres-dsn (and gda-odbc-dsn, etc) can be added acting like
this. This component should be able to build the DSN string which goes
to the gdalib config file. This could be retrieved by the app using the
component through a property.

This will avoid the user having to type the DSN string, which is
different for every provider.

So, is it a good idea?