tests: Revamp:
1) The environment manager is created in all the tests.
2) env_managment.py: when used as a library must return lists of elements.
Otherwise, it complicates the tests code unnecessarily.
Makefile: Added temporal files generated during `make check`

The option -f on `rm` makes it not to fail when no temporal files are
found. (eg, when running `make check` twice)
Merge branch 'tests_config'
Merge branch 'docs'