Add integrated spectra to Detection class

[MatthewWhiting]

From ASKAPsoft development, it would be good to have the Detection class hold the integrated spectrum. This would make it easier to record it in the case where we *don't* have access to the full pixel array.

As an aside, this would help the solution of #87. Storing the moment map would also be beneficial.

For the integrated spectra, to be complete we would need to store the peak spectrum as well, and do this for the reconstructed/smoothed array and the baseline array. The memory overheads for this should be small (a 16K spectrum, for instance, would require 384kB for all these spectra).

[paulbeartil]

hi heres the site just say paul put you onto them beartils