GFX control, no-tokio, no-async, dbus client refactor

- Working gfx modes <iGPU only, dGPU only, or hybrid>
- Add signal for gfx vendor change and make CLI wait for signal
- Add polling for led brightness to save to config
- Move daemon to zbus crate
- dbus client refactor
- Further dbus methods and updates
- Add basic notification user daemon and systemd service

ctrl-gfx/src/error.rs

@@ -0,0 +1,30 @@
+use std::error;
+use std::fmt;
+
+#[derive(Debug)]
+pub enum GfxError {
+    ParseVendor,
+    Path(String, std::io::Error),
+    Read(String, std::io::Error),
+    Write(String, std::io::Error),
+    Module(String, std::io::Error),
+    Bus(String, std::io::Error),
+    Command(String, std::io::Error),
+}
+
+impl fmt::Display for GfxError {
+    // This trait requires `fmt` with this exact signature.
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            GfxError::ParseVendor => write!(f, "Could not parse vendor name"),
+            GfxError::Path(path, error) => write!(f, "Path {}: {}", path, error),
+            GfxError::Read(path, error) => write!(f, "Read {}: {}", path, error),
+            GfxError::Write(path, error) => write!(f, "Write {}: {}", path, error),
+            GfxError::Module(func, error) => write!(f, "Module error: {}: {}", func, error),
+            GfxError::Bus(func, error) => write!(f, "Bus error: {}: {}", func, error),
+            GfxError::Command(func, error) => write!(f, "Command exec error: {}: {}", func, error),
+        }
+    }
+}
+
+impl error::Error for GfxError {}