[policy] Allow [] to document array data types for scalars as well

I don't see a reason why we should not do it like PSR5 suggests, especially because it is more consistent.

I completely support this.

Even nicer would be if we could document nested array structures beyond just array[]. But I think Php-fig and PhpDoc are not that far yet. (I personally prefer this syntax)
And ideally we should reduce the usage of these nested arrays.

I think this is fine. I also think we're already using it.

Setting up this issue as a proper coding standards change.

We should leave it at RTBC for about a week. If no one objects I'll go ahead and edit the docs standards page (node/1354) and put this in. I do not think it is controversial -- it's a clear extension of the standards we have now, and clarity is what docs are all about. Plus as I said above I think we are already using it, not sure though.

Policy is hereby adopted; https://drupal.org/coding-standards/docs#types is edited.