Change Input Settings UI flow.

1. Introduces new UI components as per the new flow
2. Temporarily disables components in the old flow that are to be
   replaced by the new flow. This is done so we can neatly revert
   to the old flow if there are issues with the new flow
3. AvailableVirtualKeyboardActivity now responds to
   android.settings.INPUT_METHOD_SETTINGS intents instead of
   InputMethodAndLanguageSettingsActivity

Bug: 25752812
Change-Id: I728d7ee185827ed328c16cb7abce244557a26518
diff --git a/src/com/android/settings/Settings.java b/src/com/android/settings/Settings.java
index edd0b4c..1c636b8 100644
--- a/src/com/android/settings/Settings.java
+++ b/src/com/android/settings/Settings.java
@@ -39,6 +39,7 @@
     public static class WifiSettingsActivity extends SettingsActivity { /* empty */ }
     public static class WifiP2pSettingsActivity extends SettingsActivity { /* empty */ }
     public static class InputMethodAndLanguageSettingsActivity extends SettingsActivity { /* empty */ }
+    public static class AvailableVirtualKeyboardActivity extends SettingsActivity { /* empty */ }
     public static class KeyboardLayoutPickerActivity extends SettingsActivity { /* empty */ }
     public static class InputMethodAndSubtypeEnablerActivity extends SettingsActivity { /* empty */ }
     public static class SpellCheckersSettingsActivity extends SettingsActivity { /* empty */ }