Update hits rotation

[lobis]

Update hits rotation inside detectorlib:

• Alternative (more clean IMHO) way to set parameters in the rml. Old syntax still works:

<addProcess type="TRestDetectorHitsRotateAndTranslateProcess">
      <parameter name="rotationCenter" value="(0,0,0)mm" />
      <parameter name="translation" value="(0,10,0)mm" />
      <parameter name="rotationZ" value="45deg" />
</addProcess>

• New parameter "rotationCenter" to specify the rotation center (defaults to (0,0,0)). Before the hits were rotation around the mean position of the hits, which does not make much sense to me as a default behaviour and this was not modifiable by the user. I was not aware of this until I looked at the code, perhaps others such as @cmargalejo are also unaware (because you mentioned to rotate the hits for the 45º rotated readout in the iaxo setup, those rotations were not done properly).

• Do not rotate especial (veto) hits. Because this process will mostly be used on TPC hits but we need to keep other hits such as veto hits, I put an explicit ignore for veto hits. This is not very clean but it works, we should probably think of a better strategy in the future to handle multiple types of "events in a single event (veto / tpc)".