Add initial support for PHP7 (#97)

* Add initial support for PHP7

* Update PHP env with now an PSR3 logger (Monolog). Now you can also create a handler function with PSR7 Http message and PSR3 logger in parameter.

* Add examples for PHP7 environement

* For development you can create a function in this path /app/userfuncdev.php it will be loaded

* Switch to alpine base image

* handler now receive an array with request, response and logger object

examples/php7/hellopsr.php

@@ -0,0 +1,12 @@
+<?php
+function handler($context){
+    /** @var \Psr\Http\Message\ResponseInterface $response */
+    $response = $context["response"];
+    /** @var \Psr\Http\Message\ServerRequestInterface $request */
+    $request = $context["request"];
+    /** @var \Psr\Log\LoggerInterface $logger */
+    $logger = $context["logger"];
+    
+    $response->getBody()->write("Hello from handler PHP");
+    $logger->warning("Hello logger");
+}