Enable tube_calib.py to calibrate several components

[KarlPalmen]

Currently in the tube calibration scripts, one can calibrate the tubes of a single component, such as the whole instrument, a door or window or an individual tube.

This is done by defining a tube specification for one component (which has one or more tubes) and passing it on to the tube_calib.getCalibration() function.

It would be useful to be able to calibrated several components together. This could be done by either enabling tube_spec to create a specification based several componenents or having a tube_caib.getCalibration function that can take several components.

The first option is simpler for the user, but the second option could be extended to allow different ideal tubes and fit parameters for different components.

Perhaps both options could be implemented.

[KarlPalmen]

This issue was originally trac ticket 6755