Ant build process changes

Robustness changes in the ant build process.
* Make sure rhino runs on 32 bit machines. Eg condition to set rhino optimization to -1 if 32bit property is set. 
* Changed rhino url.
* Remove downloaded rhino resources on clean.
* Removing xars in build on clean.
* Adding @failonerror="true" to java task in the xqlint target.
* Adding rebuild target.
* Moving check of availability of rhino and closure to dependency of get-*-target.
* Adding version to index.html and expath-pkg.xml from project.version property on build.
* Optional git.commit id in xar filename.