Add ttcn3_suites.json

[Matthias Simon]

TTCN-3 suites may require files which solely live in build directories and not in source directories. Unfortunately we don't have much knowledge about the file organization. This makes it hard to provide reliable compiler services, such as find-definition for example.

Proposal

Provide file ttcn3_suites.json which provides useful information about the build directory:

{
  "source_dir": "<path-to-cmake-source-dir>",
  "binary_dir": "<path-to-cmake-binary-dir>",
  "suites": [
    { "root_dir": "<path-to-package.yml>", "source_dir": "<optional path to ttcn3 source files" }
  ]
}