Add tools/ directory to Java extension part of project

Fixes https://github.com/crosswalk-project/crosswalk-samples/issues/12
Merge pull request #15 from crosswalk-project/tools-dir-12

Add tools/ directory to Java extension part of project
Ensure Ivy files are excluded from git repo
Update to latest stable Crosswalk

Fixes https://github.com/crosswalk-project/crosswalk-samples/issues/13
Merge pull request #16 from crosswalk-project/update-xwalk-13

Update to latest stable Crosswalk
[space dodge game] Add sample game used in 'Screens' tutorial