Include d.ts files in tns-core-modules package.
Include d.ts files in tns-core-modules package.

- Generate a combined tns-core-modules.d.ts file for user projects. (Will
be included in tsconfig.json files by the `tns` tool automagically.)
- Test the integrity of the generated combined file by compiling it.
- Remove all traces of the obsoleted tns-definitions package.

NativeScript/NativeScript,NativeScript/NativeScript,NativeScript/NativeScript,NativeScript/NativeScript,NativeScript/NativeScript