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/wamessage.h

@@ -0,0 +1,45 @@
+// defines for winamp API messages.
+
+// WM_COMMAND winamp play control messages
+
+#define WAC_PLAY		40045
+#define WAC_PAUSE		40046
+#define WAC_STOP		40047
+#define WAC_NEXT		40048
+#define WAC_PREV		40044
+#define WAC_EXIT		40001
+#define WAC_STOPFADE	40147
+#define WAC_STOPNEXT	40157
+// WM_COMMAND winamp misc control messages
+
+#define WAC_HIDEMAIN	40258
+#define WAC_HIDEPLAY	40040
+#define WAC_HIDEEQ		40036
+#define WAC_RANDOMT		40023
+#define WAC_REPEATT		40022
+#define WAC_QUIT		40001
+
+// WM_USER winamp messages
+
+#define WAU_CLEARPLIST	101
+#define WAU_STATUS		104
+#define WAU_SETPLPOS	121
+#define WAU_GETPLPOS	125
+#define WAU_TRACKLENGTH	105		// data = 1
+#define WAU_TRACKPOS	105		// data = 0
+#define WAU_GETRANDOM	250
+#define WAU_GETREPEAT	251
+#define WAU_SETRANDOM	252
+#define WAU_SETREPEAT	253
+#define WAU_GETTITLE	212
+#define WAU_PLCOUNT		124
+#define WAU_PLSAVE		120
+#define WAU_UPDTITLE	243
+
+// COPYDATASTRUCT winamp messages
+
+#define IPC_PLAYFILE 100
+
+// Playlist window WM_COMMAND messages
+
+#define PLC_SORTTITLE	40209