Allow multiple email alerts in a Proof

[#1]

Many of my users would like to be able to have Decisions and Replies to my Comments as their default email alerts in a proof but they are forced to choose one or the other. We choose Decisions and then all comments have to be @ tagged again and again and people invariably forget to @ update someone, causing confusion.

[#2]

Ability to mix-n-match from the selection would be nice to fine-tune notification levels.

[#3]

In addition, it would be great to have the notifications managed through Workfront instead of proof.