add 'to' label in front of Recipient field for better feedback
also add label for cc and bcc fields, remove placeholders
focus 'to' field automatically on clicking New message button, again
Merge branch 'master' into to-label

Conflicts:
	templates/compose.php
	templates/index.php
Merge pull request #277 from owncloud/to-label

add 'to' label in front of Recipient field for better feedback