Miscutils: fix for send_email error on DEV site

* For the DEV site send_email function was failing while trying to
  concatenate list and string (because the CFG_SITE_ADMIN_EMAIL
  was not a list).
I know it was the simplest. That was just one corner case that occurred for DEV mode.
Although I would stick to this version, just in case someone somewhere adds another address as a string because according to comments in this file, TO or BCC can be either a list or a string.
And that also solves the problem when someone puts list into ```CFG_SITE_ADMIN_EMAIL``` :)