ZENGINE: Call _system->updateScreen() every frame

Otherwise the cursor will not be updated
ZENGINE: Create class for decoding .zcr cursor files
ZENGINE: Create console command to render a cursor image to the screen
ZENGINE: Create method for cycling through all the cursors so as to identify them more easily
ZENGINE: Add a ZGI folder directory to the SearchMan
ZENGINE: Test for file.open before trying to read