Implement purging of old profiler hits

[petergrlica]

Currently the profiler requests coming into gateway are not purged in any way, so it can be a memory hog. There should be a call to action on frontend (profiler page) for the purge.

Frontend:

• [ ] simple call to backend endpoint and list clear

Backend:

• [ ] endpoint for profiler hits purging
• [ ] automatic profiler hits cleanup