Moved ImageLoader to ResourceLoader, so that loading is extensible.
i.e. here: Zed image loader now loads up a tileset instead of being a
hacked image loader.
Goal is to support more funky stuff (wad, pak .....)

The containers no longer force the user to use the ptrdiff_t type for
size information. For convenience, size() now always returns an int,
and the size_s() method offers a way to handle arrays with more than
2 billion elements. Internally, we still use ptrdiff_t, though.

Since so much code had to be changed, I took the opportunity to get
rid of capitalised accessors for classes that are lowercase.

Inverted image/all.h and thread/all.h to ensure build
Added Image::DummyFill that uses DummyImageCodec to fill empty image
Added Log:: Error/Info in image Load/Save

Lock/Unlock mechanism safer, and implement the rule of three.

objects themselves.

and the codec logic.