Allow to put markers on image for extracted spectra

[Agustin Lobo]

I do not find the way to leave a mark on the image (a vector layer) for those points from which spectra are extracted, I understand this feature does not exist and would be most useful.

[Benjamin Jakimow]

Since Version 3.3.20190331T2158.develop you can show a Speclib in a Map Canvas as followed:

• open a Spectral Library
• open a Map Canvas
• open the Map Canvas Context menu and select the Spectral Library of choice via "Add Spectral Library"

The SpectralLibrary layer will appear in the MapCanvases layer tree and can be styled like any vector layer.