autoconfiguration for mysql and postgresql databases

The following changes add support for auto-configuration for PostgreSQL and MySQL type of services on Bluemix, Pivotal, and Heroku platforms. Specifically, the PostgreSQL and MySQL service plugins added work with 1) PostgreSQL, MySQL, ElephantSQL, and ClearDB services on Bluemix, 2) ElephantSQL and ClearDB services on Pivotal, and 3) Heroku Postgres and ClearDB services on Heroku.

The PostgreSQL and MySQL service plugins have been configured with the same repository and driver version information as the Java buildpack. Also, tests are provided to simulate the different environments and services.