Upload/Download Functionality

Added download functionality
Added uploading to a processor/screen
Added prop protection to downloading and placing/uploading to a processor/screen

Notes: 
I had to store the mainfile and source code in the processor entity
I had to set the editor save file function to work with Upload and Exit
I added prop protection when left clicking on an already spawned processor/screen
The prop protection works with CPPI, if there is no CPPI then uploading and downloading still works for the owner of the entity