Implement a set of .clear() methods

Signed-off-by: Gergely Nagy <algernon@madhouse-project.org>

README.md

@@ -55,6 +55,13 @@ The plugin provides the `AlphaSquare` object, which has the following methods:
 > Almost the same as the previous function, but instead of a key, it expects a
 > 4x4 bitmap.
 
+### `.clear(key)`, `.clear(symbol)`
+### `.clear(key, col)`, `.clear(symbol, col)`
+### `.clear(key, col, row)`, `.clear(symbol, col, row)`
+
+> Just like the `.display()` counterparts, except these clear the symbol, by
+> turning the LED pixels it is made up from, off.
+
 ### `.color`
 
 > The color to use to draw the pixels.

src/Kaleidoscope/LED-AlphaSquare.h

@@ -49,6 +49,14 @@ namespace KaleidoscopePlugins {
     static void display (uint16_t symbol) { display (symbol, 0, 2); };
     static void display (uint16_t symbol, uint8_t col) { display (symbol, 0, col); };
 
+    static void clear (Key key, uint8_t row, uint8_t col) { display (key, row, col, {0, 0, 0}); };
+    static void clear (Key key, uint8_t col) { clear (key, 0, col); };
+    static void clear (Key key) { clear (key, 0, 2); };
+
+    static void clear (uint16_t symbol, uint8_t row, uint8_t col) { display (symbol, row, col, {0, 0, 0}); };
+    static void clear (uint16_t symbol, uint8_t col) { clear (symbol, 0, col); };
+    static void clear (uint16_t symbol) { clear (symbol, 0, 2); };
+
     static cRGB color;
   };
 };