smarter script for creating Android project

1、You can add the create-android-project.sh  to the PATH, so you can run it to create android project in the current directory if you like.
2、After launching the script, you can just press enter to create a default project and then call the build_native.sh to compile it.
3、Environment variables: NDK_ROOT、ANDROID_SDK_ROOT、COCOS2DX_ROOT 
are needed, or you can set them in the script.


For example:

$ create-android-project.sh 
Input package path [org.cocos2dx.demo]: 
Available Android targets:
----------
id: 1 or "android-8"
     Name: Android 2.2
     Type: Platform
     API level: 8
     Revision: 3
     Skins: WQVGA432, WQVGA400, WVGA800 (default), WVGA854, HVGA, QVGA
     ABIs : armeabi
----------
......
Input target id [1]:
Input your project name [Hello]:
Created project directory: /home/loong0/Hello/proj.android
......
Updated file /home/loong0/Hello/proj.android/proguard-project.txt

That's all.