Return an error when the form is invalid

When an invalid POST request is made, the server was crashing with the folowing
error:

"""
ValueError: The view
dashboard_app.views.image_reports.views.image_chart_settings_update didn't
return an HttpResponse object. It returned None instead.
"""

Return HTTP 400 (bad Request) instead.

Change-Id: If33b65a39f7badfc57a56230dd9d7b6bcbb86a2c
Fix group listing when group name contains dots

The name of a group can contain caracters that should not go into a URL (for
instance '.', '&', ...).

Change-Id: Ic0a69216f052b864752f416f2d30b9f603d3f112
bug #743 - sort the group members in the profile

In the profile page, the group members are now displayed as 'firstname
lastname' if available (username overwise). The list is also sorted by lastname
then firstname. Every user without first and last name will be placed at the
begining of the list.

Since python 2.2, sort is guaranteed to be stable, making the pipeline of two
dictsort sorting as expected.

Fix https://bugs.linaro.org/show_bug.cgi?id=743

Change-Id: I9d4a842062b12c8a7dfd924641ba2422598601a3
LAVA-1476: Document code standards including running dispatcher Unit ...

Update developer documentation with python 3.x and pylint.

Change-Id: I192d090def0ef12100e34f9f534887c3171452c6
Fix LAVA-1339: Worker IP address should be unique.

Introduces a dependency to 'netifaces >= 0.10.4' python module.

NOTE: Debian packaging should take care of adding the above dependency
      to lava-server package appropriately.

Change-Id: I1c03b21dc4005ef2195fb3e5015da00a62671fe9