Create new table with releases (unique combinations of PX4 release and OS release)

[LorenzMeier]

We need to be able to see the number of flights, the number of different airframes (identified by the unique ID of the MCU) and the number of hours per release and accumulated (all previous releases up to this release).

This is required to get an idea about the testing coverage we have achieved for a particular release. We might need some fuzzy matching and have two different hour counts: One for a particular minor release (1.5.2) and one for the major release (1.5), which is generally a bit more informative.