Implement raw DeviceMonitor

Multiple things have been done in this commit; the base of the new
backend has effectively been created. This branch currently has many
vital parts commented out. Therefore, this branch is currently only
intended for debugging.

src/logid/backend/raw/DeviceMonitor.h

@@ -0,0 +1,32 @@
+#ifndef LOGID_BACKEND_RAW_DEVICEMONITOR_H
+#define LOGID_BACKEND_RAW_DEVICEMONITOR_H
+
+#include <string>
+#include <mutex>
+
+extern "C"
+{
+#include <libudev.h>
+}
+
+namespace logid::backend::raw
+{
+    class DeviceMonitor
+    {
+    public:
+        void enumerate();
+        void run();
+        void stop();
+    protected:
+        DeviceMonitor();
+        ~DeviceMonitor();
+        virtual void addDevice(std::string device) = 0;
+        virtual void removeDevice(std::string device) = 0;
+    private:
+        struct udev* udev_context;
+        int monitor_pipe[2];
+        std::mutex running;
+    };
+}
+
+#endif //LOGID_BACKEND_RAW_DEVICEMONITOR_H