display: Replace hard-coded display with new config based display

Introduce a new config based system for specifying the on-screen
contents of an lcd screen.  The default screen configuration (found in
klippy/extras/display/display.cfg) is the same as the previous
hard-coded display, so this should not change behavior for existing
users.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/extras/display/hd44780.py

@@ -102,6 +102,8 @@ class HD44780:
             self.write_text(x, y, char)
             return 1
         return 0
+    def write_graphics(self, x, y, pixel_row, pixel_col):
+        pass
     def clear(self):
         spaces = ' ' * 40
         self.text_framebuffers[0][:] = spaces
@@ -187,11 +189,11 @@ HD44780_chars = [
 TextGlyphs = {
     'right_arrow': '\x7e',
     'extruder': '\x00',
-    'bed': '\x01',
+    'bed': '\x01', 'bed_heat1': '\x01', 'bed_heat2': '\x01',
     'feedrate': '\x02',
     'clock': '\x03',
     'degrees': '\x04',
     'usb': '\x05',
     'sd': '\x06',
-    'fan': '\x07',
+    'fan': '\x07', 'fan1': '\x07', 'fan2': '\x07',
 }