Unstructured interpolator (#770)

* Created the first simple implementation and tests of a class to perform linear interpolation on unstructured datapoints

* Changed structure to allow better interpolation of numpy arrays

* Added the ability to evaluate interpolation on class member functions + tests

* Added support for evaluation of ndarrays of interpolation points

* Added comments

* PEP8 fixes

* Added UnstructuredInterpolator to utils imports

* Added comments

* Added test for out of bounds behaviour

* Added filling of MC depth of maximum

* Add interpolation class and xmax to mc object

* Added rotation angle as it wasn't properly applied

* Removed printout

* Significant restructuring to remove loops in ImPACT code and speed up interpolation

* Added better support for masked arrays

* Updated minuit minisation options

* Fixed binning error when interpolating numpy arrays

* Added options for using nlopt library for testing

Added option to renomalise the likelihood to provide goodness of fit values

* Fixed error thrown by minuit

* Added option for specifying the dtype of the interpolator

* Fairly major clean up of the code, functionality remains identical

* Goodness of fit is now returned as a sum

* Fixed bug determining number of channels

* Template changes

* Removed unwanted comments

* Minor updates to mimisation and added scaling factors

* Added some pep8

* Added code for interpolation of time gradient predictions and included them in the fit

* Minor updates

* Fixed major geometry bug! Plus added new seeding options

* Added comments

* Output fixes to some minimisers

* Merge fixes

* Removed some pointless code

* Fixed some tests

* Added more tests to interpolator class

ctapipe/instrument/camera.py

@@ -167,7 +167,7 @@ def guess(cls, pix_x: u.m, pix_y: u.m, optical_foclen: u.m,
             cam_rotation=Angle(cam_rotation),
             apply_derotation=apply_derotation
         )
-
+        instance.cam_rotation = Angle(cam_rotation)
         CameraGeometry._geometry_cache[identifier] = instance
         return instance