Replace custom MS types with STL types

[SaintWish]

The types that need replacing:

• msstring - It's a C style fixed string type. Replacing it with std::string isn't advised since it's dynamically allocated. It'll probably be best to make our fix fixed string inherited from std::basic_string or use a library like this that contains a fixed string.
• msvariant - A variant variable that fits a c string, int, or float
• msstring_ref - Type defined as a const char*
• mslist - a linked list list that is used a vector throughout the code as well. Should be replaced with a std::vector or std::list depending on what should be used there.
• string_i - In debug mode, a normal string. In release mode its created within the engine and released each level
• msnew - Should probably be replaced with just new.

This should be done after angelscript is embedded.

[Aze-M]

I believe MSLists are a custom implementation of a linked list rather than a vector, would have to look into which is more efficient for our purposes.

[SaintWish]

From what I was reading traditional linked lists are bad for reading random data inside, so in such a case a vector would be better. Though I'm not sure if such would apply to mslist list since it's a custom implementation, though it might be worth it to just switch to std list in such a case.

Here's a future note: differences between vector and std list https://stackoverflow.com/questions/2209224/vector-vs-list-in-stl#2209564

Anyways, I did start doing this but I reverted it. I figured we should probably wait for angelscript to avoid breaking the already fragile scripting system.

[tschumann]

I've removed some unused bits in #268 - the rest looks reasonably set in for now.