Get timestamp for Shoutbox from the client/browser

on systems with no real time clock
Use POSIX timestamp.
Try to add a configuration variable

to enable the use of client timestamps in the chat window. Doesn't work
yet.
Merge branch 'no_RealTimeClock' of https://github.com/WIStudent/PirateBoxScripts_Webserver into WIStudent-no_RealTimeClock
Enable the possibility to get the Time from the client for shoutbox instead of PirateBox-Clock
Merge branch 'WIStudent-no_RealTimeClock' into development