Improve Android file system read performance

Faster file system read performance on Android!
 * Raw filesystem read is approximately 40% faster
 * Game startup is approximately 12% faster
 * Uses Native AssetManager
 * ... Instead of custom unzip code

Tests 
 * Tested with https://github.com/folecr/SlideShowFSTest
 * Test results are average of 3 runs
 * Tested on Galaxy Nexus with Android 4.2.2

Test 1
 * Reads image data using CCFileUtils
 * Time taken to read data
    * Before : 297.5 millis
    * After : 125 millis
 * Approximately 40% faster

Test 2
 * Creates and displays sprites from image data
 * Approximately 12% faster to display all sprites