Implement 'Create Webdriver' keyword
Support and prefer keyword arguments

Documentation also improved and added some missing test coverage
use dict argument for backwards compatibility
move some testing to unit tests

acceptance test opens browser passed to run_tests.py
test that alias is used

accidentally dropped this coverage in last commit
add missing aliases and support remote webdrivers
Merge pull request #245 from ombre42/custom-webdriver

Implement 'Create Webdriver' keyword