Android: Long press a setting to reset it

This is particularly important for game INIs, where a setting being
unset is not the same as it being set to the default value.

Source/Android/app/src/main/res/values/strings.xml

@@ -418,6 +418,9 @@ It can efficiently compress both junk data and encrypted Wii data.
     <string name="write_permission_needed">You need to allow write access to external storage for the emulator to work</string>
     <string name="load_settings">Loading Settings...</string>
     <string name="setting_not_runtime_editable">This setting can\'t be changed while a game is running.</string>
+    <string name="setting_clear_info">Long press a setting to clear it.</string>
+    <string name="setting_clear_confirm">Do you want to restore this setting to its default value?</string>
+    <string name="setting_cleared">Setting cleared</string>
     <string name="emulation_change_disc">Change Disc</string>
 
     <string name="external_storage_not_mounted">The external storage needs to be available in order to use Dolphin</string>