Add More level of Moment map

[fvitello]

The tool should support at least the following level of moment:

• Moment 0: integrated value of the spectrum (which allows you to measure the amount of gas in the line of sight)
• Moment 1: intensity-weighted coordinate (which kinda represents the velocity field of the gas)
• Moment 6: root mean square of the spectrum (basically the noise map)
• Moment 8: maximum value of the spectrum (which gives you a "peak map" to quickly spot the most prominent emission)

Level description is available here https://casa.nrao.edu/docs/casaref/image.moments.html