Define plugin building and publishing using .nosbuild

[fcturan20]

We are using CMake and C++ to build our plugins and .nospub files to publish them. Both of these are development related information and we want to support building on other languages too. Also there are some build tool related macros that can help plugin developer such as compile_definitions on C++. This issue proposes a .nosbuild file, including all these information.

This will also allow us to detect downloaded plugins and avoid creating CMake targets for them. For now, we check if the found plugin's version has build number in it but we don't want to force published plugins to have build number.

{
  "publish": {
    "release_globs": [ "Config/**"],
    "trigger_publish_globs": ["Source/**"]
   }
  "toolchain": "cmake",
  "build_only_dependencies":
  [
    { "name": "nos.plugina.sdk", "version": "1.3" }
  ],
  "toolchain_settings":
  {
    "compile_definitions":
    [
      "DEFINITION=1"
    ]
  }
}