Work on new system to allow the background job (lf_update) run without intensive locking (incomplete yet)
Bugfixes for new system to allow the background job (lf_update) run without intensive locking
Completely removed table locking in favor of transaction isolation requirements
Use different transaction isolation levels in "lf_update" program
Removed debug code in lf_update.c
Cleanup of new code for allowing "lf_update" to run without extensive locking

- Removed unnecessary variable "direct_voter_update_v" in function "forbid_changes_on_closed_issue_trigger"()
- Added PERFORM "require_transaction_isolation"() in more functions
- Integrated functions "issue_admission", "initiative_admission" and "freeze_after_snapshot" into "check_issue" function
- Removed function "manual_freeze" (replacement: set "issue" timings accordingly, when needed)
- Added/modified some comments
Removed deprecated timeline views
Removed setting of "ranks_available" column in function "clean_issue"
Update script to v2.2.0