Bundle .phpstorm.meta.php files for new expectedArguments completion

[King2500]

PhpStorm 2019.1 introduces expectedArguments and expectedReturnValues meta definitions to allow for approciate completion of constants and string values.
See official blog post here:
https://blog.jetbrains.com/phpstorm/2019/02/new-phpstorm-meta-php-features/

I went through Symfony framework/components and defined a lot of them here:
https://github.com/King2500/symfony-meta

People can fetch them via Composer now (as require-dev), but I think it would be better to have these bundled into this plugin.
Advantages:

• No need to require them in every Symfony project
• No need to have this requirement in composer.json (because it's a PhpStorm-specific thing and developers may not want to have this dependency there, when working with other developers/IDEs)

I added symfony-meta repo as git-submodule so this can be updated easily in the future (git submodule update?).

It will be built in plugin as "Library" folder, so PhpStorm can index/read meta defintions, as described here.

Examples
Here are some example screenshots where it comes in:

And also simple type mapping for standard Console helpers:

[King2500]

Ping @cedricziel @Haehnchen
What you think?

[Haehnchen]

@King2500 is a good idea, looks we can ship for a release against the new PhpStorm build.

but maybe also open an issue on the symfony project just for discussion. a composer dependency looks a way nice and easier to maintain.