Removed square brackets from uniq_ptr to introduce void as ValueType again

[AmroAlJundi]

As mention in #123, unique_ptrs inside formats had the Type[] notation. We removed this to be able to use void as a value type. With this came a bunch of other changes, mostly in the form of static checks of is_same<Type, void> around code that will fail if Type is void. Also, we added the ability to have type exceptions in the explicit instantiation generation script.

Changes:

• Removed [] from Format unique_ptr members.
• Fixed code in format constructors, readers, writers, and converters that will adjust for void value types.
• Added void as the default value of VALUE_TYPES in CMake.
• Added static asserts to make sure FormatOrderOne classes don't get instantiated with void as their value types.
• Added parameter to get_inst function in the explicit generation script that allows exceptions in type templates.
• Made void an exception of all FormatOrderOne classes.