Merge branch 'master' into DOC_plot_spectra_overlap and change
plot_spectra_overlap example, add example description and correct broken link
to plot_spectra.

(sorry for mixing a merge with another commit)

Conflicts:
	hyperspy/drawing/utils.py
Minor improvements to the plot_spectra doc
Merge branch 'DOC_plot_spectra_overlap' of https://github.com/francisco-dlp/hyperspy into DOC_plot_spectra_overlap

Conflicts:
	doc/user_guide/visualisation.rst