Allow users to better control in-app notifications

[#1]

Allow users to be able to do finer grain in-app notifications. For example, when a member of a team is assigned a task, they get a notice that "so and so, wants your team, Team_name, to work on this issue.

There can be many members of a team and they may never get assigned a particular task or issue, so these notifications are a bit superfluous to them.