Resolve "TSStatisticsManager should support saving configs"

Release notes

Instead of the "$write" hack in TQFolder, TSStatisticsManager now supports writing out configs natively. Also, an important bugfix has been implemented: the list of NPs will no longer lose entries beyond a certain string length.

Details

for the bug, see https://sft.its.cern.ch/jira/browse/ROOT-9486

Closes #99 (closed)