Introduce CLI

main: Parse args using getopt_long() in main().

Begin implementation of a CLI. It can be launched
using ./qswiki config --cli.

Allow connecting to another instance using "attach" command.
This uses Unix domain sockets, and in the future can be used
to drop caches, reload template, etc.

Closes: #21

cliserver.h

@@ -0,0 +1,16 @@
+#ifndef CLISERVER_H
+#define CLISERVER_H
+#include <thread>
+#include "cli.h"
+
+class CLIServer
+{
+  private:
+	CLIHandler *handler = nullptr;
+
+  public:
+	CLIServer(CLIHandler &handler);
+	bool detachServer(std::string socketpath);
+};
+
+#endif // CLISERVER_H