Implement receiver HID++ connect/disconnect events

Many changes were made here but that was the biggest one.

There's currently a bug where std::system_error: Broken pipe is thrown
after launching the daemon with a receiver connector.

A workaround for this bug is to simply shake the mouse while starting
the daemon. I will investigate this soon.

src/logid/backend/hidpp20/EssentialFeature.h

@@ -0,0 +1,32 @@
+#ifndef LOGID_HIDPP20_ESSENTIAL_FEATURE_H
+#define LOGID_HIDPP20_ESSENTIAL_FEATURE_H
+
+// WARNING: UNSAFE
+
+/* This class is only meant to provide essential HID++ 2.0 features to the
+ * hidpp::Device class. No version checks are provided here
+ */
+
+#include "Device.h"
+
+namespace logid {
+namespace backend {
+namespace hidpp20
+{
+    class EssentialFeature
+    {
+    public:
+        static const uint16_t ID;
+        virtual uint16_t getID() = 0;
+
+    protected:
+        EssentialFeature(hidpp::Device* dev, uint16_t _id);
+        std::vector<uint8_t> callFunction(uint8_t function_id,
+                std::vector<uint8_t>& params);
+    private:
+        hidpp::Device* _device;
+        uint8_t _index;
+    };
+}}}
+
+#endif //LOGID_HIDPP20_ESSENTIAL_FEATURE_H