add simple text to recovery UI

- recovery takes a --locale argument, which will be passed by the main

- the locale is saved in cache, in case the --locale argument is
  missing (eg, when recovery is started from fastboot)

- we include images that have prerendered text for many locales

- we split the background states into four (installing update,
  erasing, no command, error) so that appropriate text can be shown.

Change-Id: I731b8108e83d5ccc09a4aacfc1dbf7e86b397aaf
diff --git a/install.cpp b/install.cpp
index 819650e..b8f4781 100644
--- a/install.cpp
+++ b/install.cpp
@@ -277,7 +277,7 @@
 static int
 really_install_package(const char *path, int* wipe_cache)
-    ui->SetBackground(RecoveryUI::INSTALLING);
+    ui->SetBackground(RecoveryUI::INSTALLING_UPDATE);
     ui->Print("Finding update package...\n");
     LOGI("Update location: %s\n", path);