Optimize functional tests

[senky]

• Add disable_all_ads() to functional_base, but use direct SQL query instead of crawler in loop.
• Remove third parameter from create_ad in functional_base
• Remove dependency from test_adblocker_code_is_present, because it depends on test of different class
• Remove difficult readable dependency from test_past_end_date_is_not_displayed - simply create another ad, update it's end date and test it's not present
• Rationalize use of reset_groups() in hide_group_test - it needs to be called after every test, so use tearDown()
• Split acp_test, because it is too big
• Refactor acp_test (introduce get_manage_page(), get_settings_page() and submit_with_error($error_lang) (maybe we won't need to split the class after that)