Try to clean up asset folders for sample apps. (#128)

* Try to clean up asset folders for sample apps.

This removes the build step where we copy a subset of assets, and makes
it so that FilamentApp hands out a "root path" for assets. For now this
is determined based on the location of the executable. This allows
developers to launch samples from any CWD.

Closes #11

* Restore asset copy to build.

libs/utils/include/utils/Path.h

@@ -108,6 +108,12 @@ public:
      */
     Path getParent() const;
 
+    /**
+     * Returns ancestor path where "0" is the immediate parent.
+     * @return a new path containing the ancestor of this path
+     */
+    Path getAncestor(int n) const;
+
     /**
      * Returns the name of the file or directory represented by
      * this abstract pathname.