[ANNOUNCEMENTS]: Brandnew protoc-gen-php

## Problems: 

* current implementation is too hard to handle multiple files.
* hard to maintain existing sources.

so I decide to switch new one.

## Current Status:

Work in progress. Will merge end of December.

## Differences:

* improve file structures
* generate single file / multiple file. you can choose with:

````
import "php_options.proto";
//option (php).multiple_files = false;
````

* PSR-4 style class name (consider supporting PSR-0 style naming).
* generate_package options is now standard.
* adding autoloader for simple usecase.
* support insertion point
* easy to add unittest (not added yet)

## BC Breaks

* PEAR style class name are outdated. supporting it is strongly discouraged.
  * you can use existing protoc-gen-php or create your own generator with php (I'll add generator framework foreseeable future).
* remove several unused PHPFileOptions.