Interactor event OnKeyPress should be OnChar

[paskino]

We defined lots of keyboard interaction in the viewer with OnKeyPress, but most of it should be OnChar. See https://discourse.vtk.org/t/consume-a-vtk-event-in-python/13052/3

CILViewer/Wrappers/Python/ccpi/viewer/CILViewer2D.py

Line 38 in 894fc7b

self.AddObserver('KeyPressEvent', self.OnKeyPress, priority)

It would also be nice to add a function to get the observer priority, as I wrote in the discourse:

def GetObserverPriority(vtk_object, event_name: str) -> int:
    '''Given a vtk object and an event name, return the priority of the observer
    
    In Python it is impossible to get an observer from the object programmatically, 
    but the string representation of the object contains the observers with priority.

    This code reads the string representation and returns the priority as integer.
    '''
    string = str(vtk_object)

    ss = string.split("vtkObserver")

    eventObservers = []
    for s in ss:
        lines = s.split("\n")
        eo = {}
        for line in lines:
            try:
                k,v = line.split(":")
                k = k.strip()
                v = v.strip()
                if k in ['Event', 'EventName', 'Command', 'Priority', 'Tag']:
                    eo[k] = v
                    eventObservers.append(eo)
            except:
                pass

    for el in eventObservers:
        if el['EventName'] == event_name:
            return int(el['Priority'])