More natural and easier way to write C++

[gitcatrat]

Describe the project you are working on:
City builder type game with a twist. It has a lot of procedural content and mesh generation. I've used C# so far but I'd like to move most of the generation to C++. I also want to use third-party C++ libraries which are either not written in C# or are sketchy (e.g straight skeleton subdivision).

Describe the problem or limitation you are having in your project:
Writing C++ feels very unnatural in Godot, especially compared to Unreal. Writing C++ in Unreal feels like writing C# in Godot - you just create a class, write your logic and hit compile. It's done! Godot has a whole ritual dance around C++: SCons file, several text based files in Godot, third cpp file, have to mess around with terminal, etc.

Describe the feature / enhancement and how it helps to overcome the problem or limitation:
C++ should be just as easy as C# in Godot.

Describe how your proposal will work, with code, pseudocode, mockups, and/or diagrams:
Unfortunately I don't know anything about this process. But I think we'd need to define a "developer C++ land" boundary, it could be a specific directory in project root where all C++ goes (plus points for configurability). Then there should be a compile button that compiles all the C++ files in that directory. Would also be great to have an UI for generating new C++ class files with all the boilerplate already written. UI should have different options like class name, what it inherits, etc.

If this enhancement will not be used often, can it be worked around with a few lines of script?:
I think this is what everyone who write any C++ would use.

Is there a reason why this should be core and not an add-on in the asset library?:
It makes C++ development so much easier (both in effort and understandability) and faster.

[Calinou]

Duplicate of #573 and #119.