Fixes #2349. Add a macro that can be used to stop compiler warnings for unused function arguments. Saves every person from doing (void)x //Silence warning. The macro name, UNUSED_ARG, should make it obvious what is happening. Kernel instances have been updated to use it.

Fixes #2839. Make the error message from the Load algorithm much clearer if it can't find an appropriate loader.

Refs #2838: Peak object is pretty complete; some of the conversions to DSpacing and such should be checked to be sure. Tests are in place.

Refs #2650. Add abilities to the history so that any previous algorithm can be recreated plus corresponding tests."

Moved to use more of AlignDetectors for calculating tof to d conversion and added diagnostic messages. Refs #2502.