[Runtime] Fix install issue of widget applications without 'version'
attributes.

Widget application are failed to be installed without “version="xxx”
attribute in config.xml, case is same with 'name', 'description'
elements.

Root cause of this issue is Crosswalk makes WGT follow XPK manifest checking methods.

This PR is to fix above issue.

BUG=XWALK-1108
Merge pull request #1665 from shaochangbin/tags-configxml

[Runtime] Fix install issue of widget applications without 'version' attributes.