Removing un-necessary italics in latex labels

Made all unit abbreviations and text super/sub-scripts un-italicized with \mathrm, as only the labels towards the end of the file did this consistently. Left out the M in M_{\odot} as it could go either way. Also left out the subscript JL that appears on some variables, as I'm unsure of its exact meaning, and suspect italics might be appropriate here. Also left out H/L/V/E as I can see the italics looking better for single-letter detector names.