Phar Plugin

My first contribution for you, Block8.
Phar plugin #106 based ;) (created in #611)

```
phar:
    directory: /path/to/directory
    filename: foobar.phar
    regexp: /\.(php|phtml)$/
    stub: filestub.php
```

Directory: ```phar``` output directory. Default: ```%buildpath%```.
Filename: ```phar``` filename inside output directory. Default: ```build.phar```.
RegExp: regular expression for Phar iterator. Default: ```/\.php$/```.
Stub: stub content filename. No default value.

I just got the oldest issue and created the plugin. :smile: