[Android][Manifest] Support the 'icons' member

Packaging tool support 'icons' member according to the W3C specification:
http://w3c.github.io/manifest/#icons-member

BUG=https://crosswalk-project.org/jira/browse/XWALK-2023
Merge pull request #2164 from jinbang/tool_support_manifest_icons

[Android][Manifest] Support the 'icons' member