Using absolute path to call the scenario scripts.

Playing around with bash to get the absolute path to the run_tests
script, and from there calculate the path to the script.
The motivation of this, is to allow this script to be run from either
the test directory, or from any other place.
Add utils library, which should contain a collection of common functions.

Right now, the library only contains a way to get the current repository
(by reading repository.txt), so it can be used from the scenarios to
simplify the user's life.
Changes to not show the absolute path to scripts to the user.

When any scenario is called with an absolute path, this script (used
from the scenarios to place the information in the screen) will print an
absolute path too. I have just changed that, to show only the script
name.
Some identation changes.

Substituting \t by spaces.
Removed lib/utils.bash

Didn't use it in the end as I suppose I would, so I'm removing it.
Adding /tmp prefix, to force the creation of the repos in /tmp