[client_icons] Refactor Plugin

- Use IconTheme
- Add/Remove some clients

clients_icons/hicolor/index.theme

@@ -0,0 +1,28 @@
+[Icon Theme]
+Name=hicolor
+Comment=Icons for XMPP Clients
+
+# Directory list
+Directories=16x16/apps,22x22/apps,32x32/apps,scalable/apps
+
+[16x16/apps]
+Context=Applications
+Size=16
+Type=Fixed
+
+[22x22/apps]
+Context=Applications
+Size=22
+Type=Fixed
+
+[32x32/apps]
+Context=Applications
+Size=32
+Type=Fixed
+
+[scalable/apps]
+Context=Applications
+Size=16
+MinSize=8
+MaxSize=512
+Type=Scalable