Reworked the DaemonCommand.

* Accepts options for PID and log file.
* Uses posix_kill whenever available.
* Checks that the daemon actually started or stopped.
* Try to terminate then kill the daemon.
* Uses the logger or output instead of "echo".

Added a ProcessControl interface and implementations.

Closed #908

Tests/PHPCI/ProcessControl/UnixProcessControlTest.php

@@ -0,0 +1,22 @@
+<?php
+namespace Tests\PHPCI\ProcessControl;
+
+use PHPCI\ProcessControl\UnixProcessControl;
+
+class UnixProcessControlTest extends ProcessControlTest
+{
+    protected function setUp()
+    {
+        $this->object = new UnixProcessControl();
+    }
+
+    public function getTestCommand()
+    {
+        return "read SOMETHING";
+    }
+
+    public function testIsAvailable()
+    {
+        $this->assertEquals(DIRECTORY_SEPARATOR === '/', UnixProcessControl::isAvailable());
+    }
+}