Fixes 801687 - Upgrade bouncer database handling

* Implements PDO instead of old mysql_* API
* Adds error handling, raises exceptions on failure
* Adds new tests for new database layer which all pass (YAY!)
* Fixes older tests that rely on old SDO database object.
* Creates mock Memcache object and interface for caching layer.
Merge pull request #26 from brandonsavage/database-upgrade

Fixes 801687 - Upgrades bouncer database handling to use PDO. Database tests pass.
per-line timestamping, and elapsed time at end... helps with debugging
log_this call has to come before db update or it only echos, doesn't write to db
Adding a robots.txt file - fixes bug 892189