Update description

This update includes all submissions until 7 May 2015 from the 2015 Emission Reporting Round
--> Main pollutants and PMs were gridded on SNAP sector level for the years 1990 to 2013 with the latest available submissions
--> HMs (Cd, Hg, Pb) and POPs (PCDD/PCDF, B[a]P, B[b]F, B[k]F, Indeno and HCB) were gridded on GNFR14 sector level for the year 2013 with the latest available submissions