Printing/saving total number of counts used for imaging

[paolomassa]

I think it would be nice to have this information printed and saved somewhere, like it is done in the IDL version. We use it a lot to have an idea about the reliability of the reconstructions. Maybe we could print this information here

stixpy/stixpy/calibration/visibility.py

Lines 72 to 92 in d8ca4e1

	def create_meta_pixels(pixel_data, time_range, energy_range, phase_center, no_shadowing=False):
	r"""
	Create meta-pixels by summing data with in given time and energy range.
	Parameters
	----------
	pixel_data
	Input pixel data
	time_range :
	Start and end times
	energy_range
	Start and end energies
	phase_center
	The coordinates of the phase center
	no_shadowing : bool optional
	If set to True turn grid shadowing correction off
	Returns
	-------
	`dict`
	Visibility data and sub-collimator information
	"""