Logging should be in memory until a test completes

[end2endzone]

The logging mecanism is way too slow. The current implementation opens and closes the file each time an arduino function is called which is not effective with arduino functions that are time based (calls millis() multiple times).

A possible implementation would be to log every calls to memory and flush the memory to file when eixting the program or when changing the log filename. This would greatly speed up the process.