Add support for setting up and tearing down applications

[petermasking]

Currently there is no way to set up the application context (like connection to the database) before starting the server. The same goes for tearing down the application (closing the database connections). We need to support both in order to build full functioning applications.

The idea is to configure set up and tear down scripts per service as follows.

{
    "url": "http://127.0.0.1:3000",
    "setUp": "./setUp",
    "tearDown": "./tearDown",
    "standalone": {}
}

This way, each service can be configured differently.