Changes to be committed:
	modified:   src/analyserwindow.cpp
	modified:   src/analyserwindow.h
	modified:   src/analyserwindow_errors.cpp
	modified:   src/analyserwindow_signal.cpp
	modified:   src/analyserwindow_signal_click.cpp
	modified:   src/analyserwindow_signal_data.cpp
	modified:   src/analyserwindow_signal_file.cpp
	modified:   src/kzlist.cpp
	modified:   src/linedata.cpp
	modified:   src/linedata.h
	modified:   src/lineio.cpp
	modified:   src/outputwindow.cpp
	modified:   src/xgspectrum.cpp

* Fixed critical bug in error handling. Error objects are now caught as
  "catch (Error &e)" rather than "catch (Error *e)" previously.

* Added Changed flag to LineData which is set true when the object's Selected
  status is changed. This allows the most recently changed object to be
  identified upstream in AnalyserWindow.

* Using the Changed flag, the most recently toggled plot is identified in
  AnalyserWindow::on_click_plot. This line is then de-selected in all other
  spectra to ensure that no line can be selected more than once.
Minor improvements to the graph object. Changed K unit to cm-1 where it was quoted.