Adding some additional information why some plots were not produced

[heavelock]

From my point of view, as a new user of MSNoise, there is quite a few things during plotting that are unclear. For example, it's very often for MSNoise to stop executing script due to lack of a file and not returning information about that to the user. One of the examples is dtt plot that prints a name of a file from MWCS directory but after a while quits(line 68) without any information in case there is no file containing DTT results.

I think we should add some verbosity in situations when execution of script is executed to provide some more information to user.