setup.py: try-except non existing files

The setup.py generates description content based on certain files. These files
are not existant when Python is installed from Pypi, though. Because they are
also not important for the current monk installation, the setup.py's read
method fails silently in these occasions now.

See GitHub Issue #89.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
docs: Inform about how to always tear_down()

In recent examples it was not shown that the Fixture's tear_down() method might
not be reached and executed at all, if a test does not explicitely states so,
therefore the example in the documentation had to be adapted.

See GitHub Issue #90.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
fixture.py: Add test connections

The test connections are now added by default and can be activated via fixture
files.

See GitHub Issue #91.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
fixture.py: Rename Layer's Base Exception

was a copy&paste error that was not seen before.

See GitHub Issue #92.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
fixture.py: provide a simple cmd() interface

I assume that most test cases will only work with a single device, therefore
having an interface, like:

    fixt.devs[0].cmd(...)

Is awful! It is better to provide this as a single method directly in the
fixture object, like:

    fixt.cmd(...)

which does the exact same thing.

This is what is implemented here.

See GitHub Issue #93.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>
fixture.py: Add Debug Message after updating Props

For better debugging of fixture files it is necessary to have a little more
debug information.

See GitHub Issue #94.

Signed-off-by: Erik Bernoth <erik.bernoth@gmail.com>