Provide timestamp to handle() method of plugins
Provide timestamp to handle() method of plugins

The abstract method signature of the method handle() on
statscache.plugins.BasePlugin includes a timestamp, but this is not actually
given when the method is invoked. This change adds that, and a corresponding
change in statscache_plugins corrects the method signature in the plugin
implementations.

yazman/statscache,yazman/statscache,yazman/statscache