icons: rename slider icons to more logical names

Origin commit data
------------------
Branch: ni/coolstream
Commit: cd539af1f7
Author: vanhofen <vanhofen@gmx.de>
Date: 2017-09-14 (Thu, 14 Sep 2017)

Origin message was:
------------------
- icons: rename slider icons to more logical names

------------------
No further description and justification available within origin commit message!

------------------
This commit was generated by Migit

data/icons/slider/Makefile.am

@@ -1,9 +1,9 @@
 installdir = $(ICONSDIR)
 
 install_DATA = \
-	volumebody.png \
+	slider_alpha.png \
-	volumeslider2.png \
+	slider_blue.png \
-	volumeslider2alpha.png \
+	slider_body.png \
-	volumeslider2blue.png \
+	slider_green.png \
-	volumeslider2green.png \
+	slider_inactive.png \
-	volumeslider2red.png
+	slider_red.png

src/gui/widget/icons.h

@@ -177,12 +177,12 @@
 #define DUMMY_ICON			"dummy"
 
 /* sliders */
-#define NEUTRINO_ICON_SLIDER_BODY	"volumebody"
+#define NEUTRINO_ICON_SLIDER_BODY	"slider_body"
-#define NEUTRINO_ICON_SLIDER_INACTIVE	"volumeslider2"
+#define NEUTRINO_ICON_SLIDER_INACTIVE	"slider_inactive"
-#define NEUTRINO_ICON_SLIDER_RED	"volumeslider2red"
+#define NEUTRINO_ICON_SLIDER_RED	"slider_red"
-#define NEUTRINO_ICON_SLIDER_GREEN	"volumeslider2green"
+#define NEUTRINO_ICON_SLIDER_GREEN	"slider_green"
-#define NEUTRINO_ICON_SLIDER_BLUE	"volumeslider2blue"
+#define NEUTRINO_ICON_SLIDER_BLUE	"slider_blue"
-#define NEUTRINO_ICON_SLIDER_ALPHA	"volumeslider2alpha"
+#define NEUTRINO_ICON_SLIDER_ALPHA	"slider_alpha"
 
 #define NEUTRINO_ICON_BUTTON_MUTE_ZAP_ACTIVE "mute_zap_green"
 #define NEUTRINO_ICON_BUTTON_MUTE_ZAP_INACTIVE "mute_zap_gray"