Turning off caching etc should remove data

[Zugschlus]

Hi,

when turning off a cache mechanism, etc, the program should clean up transient data at least optionally. In the cache case, it is clear that the entire cache can go once the cache is disabled. This will probably not hold for, e.g., a bayes based spam filter where losing the data might harm the plugin after turning it on again.

This is important because these data sets can be large.

Greetings
Marc