Added options to specify a window of time to look for data. (-0 and -1)

Database queries are handled by the library "libwanetmondb.pm", which
automatically gets the data from the ops DB or the datapository DB as
appropriate.

Queries to the datapository take a LONG time. The following
run took over an hour. The dstsite_idx (or srcsite_idx?) should be
added to the Datapository to make this faster. The ops DB is significantly
faster with this change.
  perl goodnodes.pl -e tbres/pelabbgmon -0 1167609600 -1 1167639600 5