feat(core): provide support for relative assets for components

Assets defined for `templateUrl` and `styleUrls` can now be loaded
in relative to where the component file is placed so long as the
`moduleId` is set within the component annotation.

Closes #5634

Closes #5634

modules/angular2/src/facade/lang.dart

@@ -72,6 +72,30 @@ class StringWrapper {
     return s == s2;
   }
 
+  static String stripLeft(String s, String charVal) {
+    if (isPresent(s) && s.length > 0) {
+      var pos = 0;
+      for (var i = 0; i < s.length; i++) {
+        if (s[i] != charVal) break;
+        pos++;
+      }
+      s = s.substring(pos);
+    }
+    return s;
+  }
+
+  static String stripRight(String s, String charVal) {
+    if (isPresent(s) && s.length > 0) {
+      var pos = s.length;
+      for (var i = s.length - 1; i >= 0; i--) {
+        if (s[i] != charVal) break;
+        pos--;
+      }
+      s = s.substring(0, pos);
+    }
+    return s;
+  }
+
   static String replace(String s, Pattern from, String replace) {
     return s.replaceFirst(from, replace);
   }

modules/angular2/src/facade/lang.ts

@@ -166,6 +166,30 @@ export class StringWrapper {
 
   static equals(s: string, s2: string): boolean { return s === s2; }
 
+  static stripLeft(s: string, charVal: string): string {
+    if (s && s.length) {
+      var pos = 0;
+      for (var i = 0; i < s.length; i++) {
+        if (s[i] != charVal) break;
+        pos++;
+      }
+      s = s.substring(pos);
+    }
+    return s;
+  }
+
+  static stripRight(s: string, charVal: string): string {
+    if (s && s.length) {
+      var pos = s.length;
+      for (var i = s.length - 1; i >= 0; i--) {
+        if (s[i] != charVal) break;
+        pos--;
+      }
+      s = s.substring(0, pos);
+    }
+    return s;
+  }
+
   static replace(s: string, from: string, replace: string): string {
     return s.replace(from, replace);
   }