Run nosetests for any environment

This PR adds a script to be able to run the integration tests on any db cluster (test, integration or production). It also removes an unused variable.

This wasn't put as a buildout part because we need to assure that the configuration is reset after the command. The `collective.recipe.cmd` would not allow that.

Note: this should only be used in your working directory and it's in preparation to do deploys directly from the working directory.

**For this to work, you need to adapt your personal ~/.pgpass file. It has to include access information for all clusters (add `pgcluster0i` and `pgcluster0`)**

Usage:

To run against test cluster: `./nose_run.sh` (same as `buildout/bin/nosetests`)
To run versus integration cluster: `./nose_run.sh -i`
To run versus production cluster: `./nose_run.sh -p`