Plugins are available even though they should not when using a more recent database version

[Andreas Preikschat]

Hello,

1) Increase the database version of any plugin you like (e. g. songs)
2) Start OpenLP

We are telling the user that the database he is using is newer than expected and that he cannot use the database. But the corresponding plugin is still loaded. But e. g. attempting to create a new song causes a traceback.

Expected:
Plugin should not be loaded when the database version is too new. We probably should
- set the status of this plugin to "Disabled" (but we must not save this status to the config)
- grey out the plugin status combo box (settings -> Plugin List)

Cheers