Feature collimator families
We add the possibility to specify the collimator halfgaps by family. We have the following changes:
- add the possibility to pass to the model a reference file with all the collimator info except the halfgap. In this file a family for each collimator must be specified
- add the possibility to pass to the model a file containing the halfgap in sigmas/mm for each family
- the collimator files now will have to specify a parking halfgap, which acts as a maximum halfgap for each collimator (if a larger halfgap is given we use the parking one)
- we update one of the examples using the families