Folder Gallery creation on a per folder basis

[yoshnopa]

As I've described in #3708, this commit allows to create galleries from folders by setting a .forcegallery file inside of a folder, even if the setting "Create galleries from folders containing images" in the Library section is not activated.
Also, by creating a .nogallery file inside a directory, a folder is not turned into a gallery even if the setting is activated.

The check is case insensitive and the content of the file is irrelevant (although an empty file is the typical usage for such a system), in theory even a folder with that name should work. For those not familiar, on Linux, Mac and Android, files starting with a dot are hidden, so in case hidden files/folders are not set visible in your file manager, after creation this file will not show up anymore.

Closes #3708

A little Question about the translation system, I've expanded the text of an existing value (to document the behavior for the user). Do I need to mark this in some way so the translators are informed that this value needs to be retranslated/expanded? I have no idea how this system works unfortunately.

[yorks-dev]

yes this looks like the perfect feature for this app.

[WithoutPants]

A little Question about the translation system, I've expanded the text of an existing value (to document the behavior for the user). Do I need to mark this in some way so the translators are informed that this value needs to be retranslated/expanded? I have no idea how this system works unfortunately.

I believe it is marked automatically by the translation platform we use.

[stg-annon]

This would be out of scope for this PR but just something I was thinking about.

If we were to populate the .forcegallery file with metadata that stash could pick up on scan as well this could be a nice way of managing gallery folders, my first thought for data like this would be a unique identifier within the file so that on rescan stash can detect of the folder has been moved instead of creating another gallery.

[yoshnopa]

@stg-annon
As the one adding chapters to galleries and waiting for approval to add a plugin that opens gallery metadata from the comicrack standard stashapp/CommunityScripts#160 you won't see me disagree :D
Actually, I think this could be something to add to the former mentioned plugin. Just look up .forcegallery files as well as Comicinfo.xml, and dont limit it to cbz files, and treat them the same. Shouldn't be too difficult I'd say.
You can ask over on that PR/open an issue over there if you have any questions.

[ghost]

Thank you. This fix many issues i had with non zipped gallery.