Properly implement FS Handling

[BlaCoiso]

Currently File System support is nearly nonexistent, supporting just checking if a file exists, find it and load the entire file into RAM.

Basic File Stuff

• Check if a file exists
• Load a file into RAM
• Create new files
• Delete existing files
• Rename files
• Write into an existing file
• Get file info (size, attributes, name, creation/modification date, etc)
• Allow a file to be opened, then allow reading/writing a slice of the file, keep an entry about the file, etc

Directory stuff

• Support subdirectories (requires rewriting a huge part of the FS code)
• Get current directory
• Change current directory
• Create new directory
• Remove directory
• List existing directories