-pkg: Support passing manifest data via -m / --manifest
-pkg: Support passing manifest data via -m / --manifest

For testing purpose the manifest data can be passed to crosswalk-pkg
as a string. Please not that at least the xwalk_package_id field
needs to be included in the manifest data.

BUG=XWALK-5618

baleboy/crosswalk-app-tools,crosswalk-project/crosswalk-app-tools,baleboy/crosswalk-app-tools,baleboy/crosswalk-app-tools,crosswalk-project/crosswalk-app-tools,crosswalk-project/crosswalk-app-tools