Crash fixes, performance improvements and some code refactoring

[randompooper]

• Fix invalid timestamps; they were cause for ffmpeg fails
• Use ffmpeg fast (inexact) seek to process videos faster
• Parallelize clip creation for a faster pooping process
• Fix issues with ffmpeg failing by removing need for quoting file names. Thanks to this file names with spaces and quotes are supported
• Change above also introduced compatibility with Linux systems
• Remove unnecessary re-encoding for effects
• Allow all media formats supported by ffmpeg. It will be converted to mp4
• Halved chance of squidward effect being applied

Appropriate PR will be made to YTPPlusUI