Correct some files structure

[tadeubdev]

• Correct structure of some files
• Add support to .editorconfig
• Move 'upfiles/' dir to 'src/UPFiles'
• Separate html and PHP in index.php
• Moves PHP manipulation to save-files.php
• Alter composer autoload to psr-4
• Add info in README.md

[tadeubdev]

Remember to install .editorconfig to manipulate indentation correctly.