REST session timeout problem

During the testing of the Goals Management CRUD UI, we noticed that after some 20 to 30 minutes of being idle, the REST calls to the backend start failing (See BT-1066 for more details). Trying to solve this issue, we found that the issue has a wider scope than Goals Management only, and that we better address the problem at that wider scope. The problem also exists in older versions of the CMS, so we need to figure out

1) how / at what level to address it, - TBD
2) by whom to address it, - tiger team
3) and which versions to fix (maintenance). - focus on 10.0/10.1 for now.