added hashiterator, this is going to be one of the implementation classes for the upcoming value iterator
moved implementation for hashiterator to header file, introduced invaliditerator class, valueiterator now uses the hashiterator class internally
removed unique_ptr because client applications do not allow unique_ptr with unknown types
added missing methods to the hashiterator class
implementation of traverseiterator (untested)
fixed some issues with traverse iterators
first key/value pair was not correctly retrieved, this has now been fixed
update documentation about iterating
Merge branch 'master' of https://github.com/CopernicaMarketingSoftware/PHP-CPP