Update DesiredCapabilities doc comments to use .copy() in the examples.

clean up mix if tab and space characters.
Issue 6486

Signed-off-by: Luke Inman-Semerau <luke.semerau@gmail.com>
Merge branch 'master' of https://github.com/SeleniumHQ/selenium

Conflicts:
	py/selenium/webdriver/common/desired_capabilities.py
	py/selenium/webdriver/firefox/extension_connection.py