Move functions in ObjectJsonHelpers to their relevant namespaces and classes
- Move ParseColour to Colour::FromString
- Move ParseCursor to Cursor::FromString
- Move LoadStrings to StringTable::ReadJson
- Move LoadImages to ImageTable::ReadJson
- Move ParseObjectEntry to Object::ParseObjectEntry
- Move GetString, etc. to Json::GetString, etc.
- Delete ObjectJsonHelpers .cpp and .h files
Clang-format sees the text behind `#pragma region` as code and formats it. Instead of stating the copyright and date there, it's now in the comment block right below it. The text "Copyright" is left in the `#pragma region` line, as clang-format sees it as a single identifier.
I took the opportunity to normalize the dates, and add the copyright notice to the source files where it was missing them (except for third-party and the generated resources.h file).
`typedef struct/union/enum name { ... } name_again;` is not needed whe compiling C++, moving the name at the back to be in front of the object and removing `typedef` makes it usable the very same way.
This also replaces typedefs with the using keyword. They have better readability, especially for function pointer types, and would allow more flexibility when used with templates.
