update the c++ in the engine to modern c++

Here are some things that this includes (more specifics to be added later):
[ ] nullptr, not 0 as a pointer, or NULL either.
[ ] use std containers when possible: i.e. remove the `array` and `queue` classes in the e directory (these were written before the STL was available!).
[ ] change pointer types to e.g. unique_ptr.