[IP] Save filter settings per user

[sebastian-meyer]

There should be an option in the user's settings to save his/her preferred filters. Those settings should be used as a default if the user is logged in.

[matthias-ronge]

This issue also affects the current master.

[matthias-ronge]

Goal: Each user should be able to specify in his/her settings whether completed processes, or processes from deactivated projects are initially displayed or hidden after login.

(See version 2 screenshot above. This is unrelated to the filter strings, which are already stored per-user.)