BabuDB/Replication: added some mechanism to the plugin-architecture to...

BabuDB/Replication: added some mechanism to the plugin-architecture to restrict the usage of a plugin to a specific range of BabuDB versions.

git-svn-id: https://babudb.googlecode.com/svn/trunk@376 d4c7dd96-b7b2-11dd-893d-d98698f66bbf