Spectral library module revision

[Benjamin Jakimow]

• use Speclibs based on /vsimem/ (instead QgsVectorLayer with in-memory driver)

• Linux: plot window crashes (needs upcomming PyQtGraph 0.11 )

• permanent/direct editing mode for attributes now like in Vector Tables

• show geo-coordinates

• ADS FieldSpec IO (at least input) see Issue #215

• select spectral by attribute

• select spectra in plot window

• select spectra (with geo-coordinate) from map

to be discussed:

• yes delete spectra without activating editing mode explicitly?

• gpkg, single table geopackage with multi table approach?