Update build application wiki page.

1. Add "icons" key in manifest.json for Android when using Crosswalk-3, which
is caused by a bug of packaging tool.

2. The manifest feature in Crosswalk-2 is buggy. So force the developer to use
Crosswalk-3 and later instead.

3. Add a note for packaging with XDK source, which depends on the third party
library pycrypto.