Fix a little typo on the number of generate classes
Remove references to Phing

Apart from the "Customizing build" guide which needs to be completely
updated, any reference to Phing should have been removed from the
repository.
Remove references about datasql and datadump commands

The datasql and datadump commands have been deprecated.
Remove references to the old DBDesign cookbook

Since the dbd2propel command has been removed in Propel 2.0, this guide
is useless and has been still removed in 53ab611 but there were still
links pointing to it.