Updates to Hackbook and Test Script

* Removes redundant default.properties file.
* Updates Hackbook's build.xml to check for sdk.dir in environment variables (like other Sample apps).
* Changes the test config script to find the facebook SDK directory the same way that the build_and_test script does. Also removes the call to common.sh (which doesn't exist, if it was meant to do something, it should be re-added).

Some issues I'm seeing still, though, these are not caused by these changes:
* 'ant clean debug' for Hackbook fails on the command line because the R.java isn't generated with the resources which are specific to Hackbook. IntelliJ somehow generates the correct file, but ant fails.
* 'ant clean debug' failing for Hackbook (above) causes build_and_test to fail when compiling Hackbook.