Emit php-doc annotations

[mindplay-dk]

Compiled output should include php-doc annotations for things like function/method-arguments and property-types, where possible - not all types can be documented using php-doc syntax, since TS has type-features not present in php, and perhaps those type-declarations could be emitted as mixed followed by the actual type-declaration in the comment so it remains visible.

This would bring Pratphall's compiled code one step closer to hand-written quality code - since a lot of php developers may be consuming the compiled php code rather than the TS code, this is important, in the same way that the TS compiler itself strives to output developer-friendly and human-readable JS.

Note that I also recently submitted a similar request to the TypeScript team.