Happypanda in-bowser gallery finder

[Bozunee]

Addition of a searching feature that can look into a folder and show viable galleries to add into the program while acknowledging and hiding already present galleries that have already been added into happypanda.

It's been getting on my nerves as I try to add a bulk chunk of archives or folders into happypanda just to discover that after the hour long scan of each file half of the entries are already present in happypanda.