new struct classes
implement Iterator not Traversable
cleaned up class names and updated factory
added front/back methods to queue classes
stack logic is reversed, so some iterator methods must also be reveresed
make sure priority map is rewound before returning priority key
replace stack method peek() with more logical top/bottom methods
fixed prev/next doc block titles
add phpdoc to factory methods
misc doc block clean up
force offset to be an integer because testing for floats gets tricky
fixed valid() Iterator method
added missing class version static property
validate offset when reset() is called
renamed reset() method to erase() to avoid confusion with array reset()
new add() method for static list
added struct helper method
add struct class to init call
add struct tests
overhauled safe mode logic. global setting can be overridden at call time.