added some language files for emails

I haven't yet added any changes to the emails themselves, because I'm waiting for feedback
updated email text in language file
put email titles in language files.

modified programmes controller accordingly for language file changes for emails
Merge branch 'develop' of https://github.com/unikent/programmes-plant into feature/emails-to-users-311
fixed line breaks to be <br> in html emails. Added slug to url in emails
Update emails.php

Changed ```<br>``` to ```<br />```
Merge pull request #321 from unikent/feature/emails-to-users-311

added some language files for emails