Fixed stack overflow error
Tidied up javadoc and getHash method
Added delete methods
Added read method overflows for reading from input stream
Added file write methods
Added nullable annotation to file hash method
Added javadoc for private constructor
Merge branch 'feature/file-manager' into develop

* feature/file-manager:
  Added javadoc for private constructor
  Added nullable annotation to file hash method
  Added file write methods
  Added read method overflows for reading from input stream
  Added delete methods
  Tidied up javadoc and getHash method
  Fixed stack overflow error