Add option to pause pick wave / pause despatching during pick wave

To help with the accuracy on picking/packing reports it would be very handy to have the option to pause a pick wave when picking or during the packing process to allow the figures to not be skewed by people going on lunch, toilet breaks, assisting with other tasks etc. Currently, it seems if someone goes on lunch during a pick wave then this time just builds up incorrectly. There is also no way to reset a pick wave status on the PDA if you accidentally start a pick wave.