Updated selecium-webdriver to 2.43.0.

Works now with recent firefox/ubuntu.

Conflicts:
	Gemfile.lock
Delete memberships when deleting associated groups.

Conflicts:
	app/models/group.rb
Remove all memberships where belonging group was deleted.

Conflicts:
	db/schema.rb
Allow adding tracking code for webstatistics service. E.g. piwik.
add webstats_tracking_code to configuration screen (closes foodcoops#311)

Conflicts:
	app/views/admin/configs/_tab_others.html.haml
	config/app_config.yml.SAMPLE
be more robust showing config list