update dependency and plugin versions
replace deprecated method call
use java 1.6 because gwt 2.5.1 is only 1.6 compatible (2.6 than is 1.7 compatible)
update BootStrapper usage
change Widget to IsWidget for setInSlot()
make objectify code to rc1 compatible
update github-site-plugin
update appengine configuration for using hdr storage
add missing javadoc