Some basic fixes

[UserUnknownFactor]

1. Accept user:// paths, because they're just normal paths (albeit to user directory), and files containing multiple dots in name, because dots are traversal only when paired with \ or /, there can be normal paths with dots in them like no_this_is_ok..._path.png.
2. If only one ambiguous .gd in addons assign it to plugin.cfg.
3. Added #define for invalid path replacer.
4. On my system the scrolbar theme disables them altogether, so removed it.

[nikitalita]

thank you for the PRs! I’ll review these later this week

[UserUnknownFactor]

Please, for goodness sake, add these fixes yourselves if you don't accept PRs since the games I encountered were decompiled incorrectly due to the problems I highlighted here. (Like the user:\\* files were not unpacked in the first and valid names with multiple dots were replaced in the second.)

[nikitalita]

Please, for goodness sake, add these fixes yourselves if you don't accept PRs since the games I encountered were decompiled incorrectly due to the problems I highlighted here. (Like the user:\* files were not unpacked in the first and valid names with multiple dots were replaced in the second.)

My apologies, I have already added the bulk of these changes into the current master (path fixing, etc.), but I neglected to close this and let you know. Thank you for this PR!

[UserUnknownFactor]

Thank you. You can also notify people of what you do with their contributions by mentioning them in the commit title, you know.