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)

ui/button/button.android.ts

@@ -1,4 +1,4 @@
-import common = require("ui/button/button-common");
+import common = require("./button-common");
 import utils = require("utils/utils")
 
 global.moduleMerge(common, exports);