Various fixes and optimizations for PHP unit tests

- tests provide their own certificates for testing of signing functionality
- rest api tests do not rely on a working apache instance of shindig anymore. any http calls are mocked instead.
- tests work from command line. any needes $_SERVER variables are set in the tests
- tests can override the main configuration with own values
- some fixes in the provided sample json database

this also means, that we can start to include the phpunit tests as a hudson job.

if there are no objections, I'll commit this patch tomorrow (yay, my first commit :-) ) and write a small ant script for hudson.