clean up

* remove sprites and corresponding styles
* remove base pngs
* remove other unused images

htdocs/css/openwebrx-globals.css

@@ -5,21 +5,3 @@ html, body
     height: 100%;
     font-family: "DejaVu Sans", Verdana, Geneva, sans-serif;
 }
-
-.sprite {
-    background-image: url(../gfx/openwebrx-sprites.png);
-    display: inline-block;
-}
-
-.openwebrx-button.highlighted .sprite {
-    background-image: linear-gradient(rgba(255,127,0,0.5), rgba(255,127,0,0.5)), url(../gfx/openwebrx-sprites.png);
-    background-blend-mode: overlay;
-}
-
-@media only screen and (-webkit-min-device-pixel-ratio: 2),
-only screen and (min-device-pixel-ratio: 2) {
-    .sprite {
-        background-image: url(../gfx/openwebrx-sprites-2x.png);
-        background-size: 198px 77px;
-    }
-}

htdocs/css/openwebrx-header.css

@@ -195,39 +195,9 @@
 }
 
 /*
- * Sprites (images)
+ * RX details arrow up/down switching
  */
 
-.sprite-panel-status {
-    background-position: 0 0;
-    width: 44px;
-    height: 38px;
-}
-
-.sprite-panel-log {
-    background-position: -44px 0;
-    width: 38px;
-    height: 38px;
-}
-
-.sprite-panel-receiver {
-    background-position: -82px 0;
-    width: 40px;
-    height: 38px;
-}
-
-.sprite-panel-map {
-    background-position: -122px 0;
-    width: 38px;
-    height: 38px;
-}
-
-.sprite-panel-settings {
-    background-position: -160px 0;
-    width: 38px;
-    height: 38px;
-}
-
 .openwebrx-rx-details-arrow {
     position: absolute;
     bottom: 0;

htdocs/css/openwebrx.css

@@ -1291,83 +1291,10 @@ img.openwebrx-mirror-img
     margin: -10px;
 }
 
-.sprite-zoom-in {
-    background-position: 0 -38px;
-    width: 27px;
-    height: 27px;
-}
-
-.sprite-zoom-out {
-    background-position: -27px -38px;
-    width: 27px;
-    height: 27px;
-}
-
-.sprite-zoom-in-total {
-    background-position: -54px -38px;
-    width: 24px;
-    height: 27px;
-}
-
-.sprite-zoom-out-total {
-    background-position: -78px -38px;
-    width: 25px;
-    height: 27px;
-}
-
-.sprite-edit {
-    background-position: -131px -51px;
-    width: 14px;
-    height: 14px;
-}
-
-.sprite-trashcan {
-    background-position: -145px -38px;
-    width: 14px;
-    height: 14px;
-}
-
-.sprite-speaker {
-    width: 14px;
-    height: 15px;
-}
-
-.sprite-squelch {
-    background-position: -131px -38px;
-    width: 14px;
-    height: 13px;
-}
-
-.sprite-waterfall-auto {
-    background-position: -103px -53px;
-    width: 14px;
-    height: 11px;
-}
-
-.sprite-waterfall-default {
-    background-position: -117px -53px;
-    width: 14px;
-    height: 12px;
-}
-
-.sprite-bookmark {
-    background-position: -159px -38px;
-    width: 21px;
-    height: 27px;
-}
-
 .openwebrx-zoom-button svg {
     height: 27px;
 }
 
-.openwebrx-sliderbtn-img
-{
-	width: 14px;
-	position:relative;
-	top: 1px;
-}
-
-.openwebrx-slider-button img,
 .openwebrx-slider-button svg {
 	position:relative;
 	top: 1px;