AWS Credentials support, StaticCredentials Provider (#17)

* added credentials API, disabled FFI backend for now

* Added CredentialsTest

* Added support for specifying CMAKE_BUILD_TYPE on the command line

* Added support for AwsCredentials and StaticCredentialsProvider

src/AWS/CRT/Options.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace AWS\CRT;
+
+final class Options {
+    private $options = [];
+
+    public function __construct($opts = []) {
+        $this->options = $opts;
+    }
+
+    public function __get($name) {
+        return (isset($this->options[$name])) ? $this->options[$name] : null;
+    }
+
+    public function asArray() {
+        return $this->options;
+    }
+
+    public function toArray() {
+        return array_merge_recursive([], $this->options);
+    }
+
+    public function getInt($name) {
+        $val = $this->$name;
+        return (is_null($val)) ? 0 : (int)$val;
+    }
+
+    public function getString($name) {
+        return !empty($this->options[$name]) ? strval($this->options[$name]) : "";
+    }
+}