transients: user-configurable windows, and some minor things

Hi @GregAshton this is finally the first part of the merge request I've been promising since summer.

The main first commit replaces the boolean 'transient' flag of the main classes by transientWindow, t0band, tauband. The main use case is a coherent grid search; I hope I've managed to put sane defaults to all other use cases, but not 100% sure I haven't overlooked any in the semicoherent/glitch world, so it's definitely worth a careful look from you.

Next commit suppresses transient parameters from the injection .cff file if window=none, which I think I needed to fix some data-reuse corner cases, though I can't remember anymore quite which cases those were. Still seems reasonable to do, though...?

Third commit just updates an example.

I split this off from my devel branch; the next part will require a small filepointer handling fix in lalpulsar, and for the final one (where this is all leading to) I need to clean up my CUDA code. I'll make separate merge requests when ready.