README:adds a list of extra VLKB-features over standard SODA

README.md

 ## vlkb-soda
 
-is a web-application to access astronomical data stored in FITS-files. It consists of
+is a web-application to access astronomical data stored in FITS-files.
+It implements SODA IVOA recommendation v1.0 (https://ivoa.net/documents/SODA/20170517/index.html).
+Additionally to SODAv1 it also provides VLKB-specific functions:
+
+- the filtering paramters (POS, BAND) can be given in GALACTIC and VELO-LSRK-km/s coordinates systems
+- supports non-WCS cuts by pixels grid
+- inserts additional metadata (RESTFREQ, CUNIT) if not present in FITS-headers
+- can create and hold a cut-file server-side for later download, and
+- provides count of undefined values in the cut-file
+
+
+The service consists of
 
 - **vlkb-soda** web-application and associated **vlkbd** daemon to access FITS file contents based on VO SODA
 - **vlkb** command line utility to perform some of the functionalities of the web-applications on command line