#35 source info

[david hanley]

For the source info object, allow the user to request
the appropriate level of detail; this could mean just
name of the source, the fields, the stats, or a sample.
Do this with a series of flags that can be binary
or-ed. Use this for the getSourceInfos object, so we
can get just the names of all the sources on the server
if we like, or the full stats for everything.