Exchange OWA support in Rambox

How to use:

1. Choose _Custom Service

• Name: Whatever you like
• URL: https://[your.domain.com]/owa/
• Logo: https://www.jwcc.edu/files/Information_Technology/images/outlook2k13logo.png, though you can use any you like.

2. Open Advanced and use these Custom Codes (depending on your feature preferences):

• Unread count only, immediately updated - paste the contents of unread-notification.js
• Unread count, incoming mail and calendar reminder notifications - paste the contents of new-mail-notification.js

Ideas and pull requests are welcome.