[Pending] Allow processing of DVB EPG data before it is written to the database (1 Viewer)

[ollienator]

A small patch to allow plugins to process new EPG data before it is written to the database.
This is especially useful to filter out corrupt EPG data, handle encoding issues in received EPG data, etc.
The current implementation raises the OnImportEpgPrograms event after commiting new data, so in order to make any changes, the database needs to be accessed again.