SeleniumTestCase moved, add multiple webdrivers

SeleniumTestCase moved to dedicated file seleniumtests.py
Removed driver class variable
Added support for multiple webdrivers
Selenium rework

Make each app within adagios run it's own browser session.
Initial work to allow for testing multiple browsers in the same run.
Invalid variable name access_keys, fixed
Skip selenium for pull requests from forks
Remove unused imports and move imports to top
Initialize fake adagios env after selenium

If selenium initialization failed the fake adagios env would not
be destroyed leaving nagios daemon processes hanging around.
Make selenium tests skip if there is an error

Wrapped webdriver initialization in a try/except and skip if unable
to initialize the webdriver in use.

Running with "python manage.py test -v 2" will show the reason for
skipping.
Merge pull request #457 from opinkerfi/selenium_rework

Selenium rework