add foodcoop configuration screen
don't fail in foodsoft_config without database,

and use proper config defaults so that configuration editing has
sensible default values
hide protected keys from config
let plugins define their own foodcoop-config defaults
allow to specify (un)checked values for config boolean

Conflicts:
	app/helpers/admin/configs_helper.rb
allow protected keys to be set/unset + config_db tests
fix deprecation warning
specify timezone in configuration (closes foodcoops#282)