edify extensions for OTA package installation, part 1

Adds the following edify functions:

  mount unmount format show_progress delete delete_recursive
  package_extract symlink set_perm set_perm_recursive

This set is enough to extract and install the system part of a (full)
OTA package.

Adds the updater binary that extracts an edify script from the OTA
package and then executes it.  Minor changes to the edify core (adds a
sleep() builtin for debugging, adds "." to the set of characters that
can appear in an unquoted string).
diff --git a/install.c b/install.c
index eff9312..0b5c04d 100644
--- a/install.c
+++ b/install.c
@@ -256,7 +256,7 @@
     int status;
     waitpid(pid, &status, 0);
     if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
-        LOGE("Error in %s\n(Status %d)\n", path, status);
+        LOGE("Error in %s\n(Status %d)\n", path, WEXITSTATUS(status));
         return INSTALL_ERROR;
     }