Use a 3 hour timeout for tasks browse cache
Merge branch 'issue-query-perf-improvements' of https://github.com/PyBossa/pybossa into issue-query-perf-improvements

* 'issue-query-perf-improvements' of https://github.com/PyBossa/pybossa:
  use sql count for task_run with the new tests
  corrections in anonymous and authenticated tests for old count method
Remove unused session