moves the confirm close callback from index.html into HLManager

introducing use of settings:  'helios.browser.showDocOnOpen' and 'helios.confirmOnClose' taking as default the values of previous versions and making persistent the last used preference

'devel' using ['amdconfig:helios']
using #settingValue

removes 1 space
using `'helios.confirmOnClose' settingValueIfAbsent: true`