Move Scheduling Settings to User Settings, change defaults

[#1]

Right now, the settings for staffing is in a tiny cog in the upper-right-hand corner of the staffing tab. This would make sense if these were related only to the project. However, these should be in a sub-category in the user's settings.

Also, it would be preferred if "Limit Assignments to the Group associated with the Project" was deselected as the default.