export symbols from gravity-executable so native modules can access functions.

[tDwtp]

In #374 I reworked some parts.
I now export to lib*.a/*.lib of the executable so people can link against something.

I cleaned up the build-results. If you don't like it, let me know. They are placed depending on the build configuration. /(Configuration)/* if non defined they are placed where they would be expected (/bin and /lib and not split, seemingly randomly to /bin /src /lib) However I would like to split static libraries to /lib and dynamic libraries to /dyn (or something). But I left that out for now.

I reworked the headers, so they can be handed out with one exception: gravity_core.h. They would be very helpful, but are not necessary.

A list of Headders to hand out to developers:

• gravity_array.h
• gravity_compiler.h
• gravity_config.h
• gravity_core.h
• gravity_debug.h
• gravity_delegate.h
• gravity_hash.h
• gravity_json.h
• gravity_macros.h
• gravity_opcodes.h
• gravity_utils.h
• gravity_value.h
• gravity_vm.h