icecube/flarestack: Titan V2.2.6

The main changes to V2.2.5 are

• the time PDF DecayPDF is fixed now (the weighting for injection was not done right in DecayPDF.effective_injection_time())
• the submission script that is produced to submit jobs to the DESY cluster has been moved to the scratch space
• the Point Source Tracks v002_p03 are now implemented
• the get_rate() function in cosmo/rates/ can now give the uncertainty of the rate where available
• all the analysis scripts for the correction of the supernova stacking analysis are updated