[Enhancement] [Metadata Utilities] Option to remove unwanted items on metadata update.

[HerrKnarz]

Metadata addons often add tags, features and other items, the user doesn't want. Since most addons don't provide an option to disable certain tags, we need an option to remove them after metadata updates in Metadata Utilities:

• Provide a blacklist and possibly regex option
• Provide a whitelist with option to add all existing. Maybe tricky to keep the list in sync with the Playnite database, if that's even desirable. Maybe updates to the list should only be made manually.
• Black and Whitelist can be used at the same time, but in that case the whitelist only defines items that will never be removed, even if not in use.
• Option to put items on blacklist when removing them in Metadata Editor
• Settings tab to edit the lists: Add a simple textbox with comma separated values for each type and use the select metadata item dialog to add or remove items from that list. Provide a toggle, if the whitelist means "remove all others" for each item type.

[HerrKnarz]

I decided to postpone the whitelist option indefinitely. I don't think it's really necessary. Regex will also follow later, when I add that to merge rules as well.