CAL-943 Agenda invitation sends an email with a 0 bytes .ics file

Fix description: in sendMail function, create ics file outside the loop of users and create attachment inside the mail of each participant.
CAL-754	No translation of participation status

Fix description:
- i18n participant status.
- add key for Pending status.
CAL-721 [Share Calendar] Concatenate the resource bundle keys for translation purpose
Merge commit '2c99f5a499522490d3f1e9106f805ef4c178025e' into HEAD