Add instructions to read a file and write to a file

These instructions will deal with files and the various things surrounding them. For example, an instruction to read from a file might be readf and an instruction to write to a file might be writef. Another thing to consider is the support for multiple file streams. The readf instruction needs one parameter, the name of the file. The writef instruction needs two parameters: the name of the file and the content to write. This content may need to be a string, but this can be changed.