Added pond command line application

Pond is a command line application to maintain a local filesystem cache
of data from an Enhydris server.
Added fordonia command line application

Fordonia is a command line application that performs time series
aggregation.
Fix file permissions - pond is executable
Python 3 fixes
Update CHANGES.txt
Add pond and fordonia to scripts
Windows fixes

Added pond and fordonia to Windows installer; renamed Windows installer
package to pthelma instead of loggertodb.