Add frame python binding

Add a python binding for the frame class.

Usage is as follow:

import lima, numpy

frm = lima.Frame(10, 10, lima.Pixel.BBP64F)

# metadata are readonly and are usually set by the acquisition
print(frm.metadata)

# append a key value to the attribute dict
f.attributes.update({"test": "hello, world!"})

# manipulate the data with numpy
data = numpy.array(f, copy=False)
print(data)

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