Tidy up data structure

[PaoloGB]

Modify the data structure of the TLU from the current one

to
Evt Type 6 bits: accomodate for future modification of the firmware allowing to have information on spill, etc
Input trig 8 bits: these bits indicate which of the trigger inputs fired. At the moment it is unlikely that we will produce a TLU with more than 8 trigger inputs so those bits can be assigned to other purposes.
Coarse timestamp (25 ns) 50 bits: Increase the time before the coarse counter rolls-over.