Preserve old DataPack behavior when overwriting data (#848)

* Match old DataPack behavior when overwriting data

* Make RemoveItem more flexible

* Ditch implied RemoveItem behavior & asher fixes

* KyleS nits - but fixed before he says them

* Add back implicit behavior

* Update CDataPack.cpp

Committing to the spec.

* Update CDataPack.h

* fixup removing last item if explicitly requested

* Fix logic for accepting pack pos, rather than index

* Fixup IsReadable

* headache is over now

core/logic/CDataPack.h

@@ -76,6 +76,7 @@ public:
 	void Initialize();
 	inline size_t GetCapacity() const { return this->elements.length(); };
 	inline CDataPackType GetCurrentType(void) const { return this->elements[this->position].type; };
+	bool RemoveItem(size_t pos = -1);
 private:
 
 	typedef union {