Improve data collection

[gartens]

• Do not record the same execution time twice for the same query
• Add a 30 second timeout to HTTP requests by the StatusGatherer. Sometimes the internal webserver in Polypheny crashes without cleaning up the listening socket, this would cause the status gatherer code to hang indefinitely
• Collect various cache sizes after the warmup phase

[vogti]

Thx, @gartens, for this PR!