Implement XDG compliance, logging, and improved 401 error handling

- Install to ~/.local/bin/winamp-mpris
- Use ~/.local/state/winamp-mpris/bridge.log for logging
- Use $XDG_RUNTIME_DIR/winamp-mpris.pid for PID management
- Add detailed user notification for 401 Unauthorized errors
- Add install.sh for automated, standard-compliant setup
- Include Winamp Web Interface source code and installer in repository

Wawi Source/plugin.h

@@ -0,0 +1,14 @@
+typedef struct {
+	int version;
+	char *description;
+	int (*init)();
+	void (*config)();
+	void (*quit)();
+	HWND hwndParent;
+	HINSTANCE hDllInstance;
+} winampGeneralPurposePlugin;
+
+#define GPPHDR_VER 0x10
+
+extern winampGeneralPurposePlugin *gen_plugins[256];
+typedef winampGeneralPurposePlugin * (*winampGeneralPurposePluginGetter)();