Add display page abstraction (#435)

tests/test1.yaml

@@ -1007,6 +1007,14 @@ fan:
       medium: 0.75
       high: 1.0
 
+interval:
+  - interval: 10s
+    then:
+    - display.page.show: !lambda |-
+        if (true) return id(page1); else return id(page2);
+    -  display.page.show_next: display
+    -  display.page.show_previous: display
+
 display:
 - platform: lcd_gpio
   dimensions: 18x4
@@ -1037,8 +1045,14 @@ display:
   model: "SSD1306 128x64"
   reset_pin: GPIO23
   address: 0x3C
-  lambda: |-
-    it.rectangle(0, 0, it.get_width(), it.get_height());
+  id: display
+  pages:
+    - id: page1
+      lambda: |-
+        it.rectangle(0, 0, it.get_width(), it.get_height());
+    - id: page2
+      lambda: |-
+        // Nothing
 - platform: ssd1306_spi
   model: "SSD1306 128x64"
   cs_pin: GPIO23