Fix location of icon and specify full Exec path (Fixes: #59)

snap/gui/riseup-vpn.desktop

@@ -6,9 +6,9 @@ Comment=Anonymous VPN
 Comment[es]=VPN Anonima
 Comment[de]=Anonymous VPN
 Path=/snap/bin
-Exec=riseup-vpn.launcher
+Exec=/snap/bin/riseup-vpn.launcher
 Terminal=false
-Icon=/snap/riseup-vpn/current/snap/gui/riseupvpn.svg
+Icon=/snap/riseup-vpn/current/snap/gui/icon.svg
 Categories=Network;Application;
 StartupNotify=true
 Keywords=VPN;riseup;leap