Read Spectra Vista Coorp (SVC) Spectrometer files

[jakimowb]

Allow to reads profile files (*.sig) created with SVC spectrometers

• return reference, target and, if available, reflectance profiles
• return SVC specific metadata
• return picture path
• relates to unified spectral profile handling #991

[janzandr]

I would recommend to structure all spectral profile import functionality in a way, that it is easy to also wrap it into individual processing algorithms (e.g. for ASD, SVC etc. spectrometers). Place algorithms here: