[Android] Minify and obfuscate the javascript and css.

This patch is to minify and obfuscate the javascript and css
files before doing packaging.
Integrate the yui compressor with the packaging tool.
Yui compressor was gotten from http://yui.github.io/yuicompressor/
The license is BSD.
Merge pull request #1485 from wuhengzhi/compress_js_css

[Android] Minify and obfuscate the javascript and css.