Implement UI scaling and more (#501)

**New Features**
 * Runtime font accessors and new symbol fonts for text, launcher, statusbar, and shared icons.
 * Added font height base setting to device.properties
 * Text fonts now have 3 sizes: small, default, large

**Improvements**
 * Renamed `UiScale` to `UiDensity`
 * Statusbar, toolbar and many UI components now compute heights and spacing from fonts/density.
 * SSD1306 initialization sequence refined for more stable startup.
 * Multiple image assets replaced by symbol-font rendering.
 * Many layout improvements related to density, font scaling and icon scaling
 * Updated folder name capitalization for newer style

TactilityKernel/bindings/root.yaml

@@ -0,0 +1,8 @@
+description: Represents root node of a device tree. It holds all other nodes.
+
+compatible: "root"
+
+properties:
+  model:
+    required: true
+    description: the name of hardware, usually vendor and model name