Change from "classic" TS 1.6 imports to the default resolution scheme.

- Use relative imports in place of most of our absolute ones.
- Add "private" ambient modules for modules that we need to import using
an absolute path (e.g. when app/.../test-something.ts needs to import
ui/styling/style-scope)

text/formatted-string.android.ts

@@ -1,4 +1,4 @@
-import formattedStringCommon = require("text/formatted-string-common");
+import formattedStringCommon = require("./formatted-string-common");
 import spanModule = require("text/span");
 
 global.moduleMerge(formattedStringCommon, exports);
@@ -26,4 +26,4 @@ export class FormattedString extends formattedStringCommon.FormattedString {
         }
         this._formattedText = ssb;
     }
-}
+}