Refactors SourceViewController into dedicated tab

* Updates UI to use source icons + tint colors
* Adds Edit button + swipe actions

AltStore/Resources/Assets.xcassets/Tabs/Sources.imageset/Contents.json

@@ -0,0 +1,26 @@
+{
+  "images" : [
+    {
+      "idiom" : "universal",
+      "filename" : "Combined Shape.png",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "Combined Shape@2x.png",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "universal",
+      "filename" : "Combined Shape@3x.png",
+      "scale" : "3x"
+    }
+  ],
+  "info" : {
+    "version" : 1,
+    "author" : "xcode"
+  },
+  "properties" : {
+    "template-rendering-intent" : "template"
+  }
+}