Change the (dodgy) seqnumfrequency variable to have ms resolution instead of second...

Change the (dodgy) seqnumfrequency variable to have ms resolution instead of second resolution.

Rename the variable to SeqnumInterval for
1, it is an interval and not a 1/interval unit
2, so that we catch when people use this old variable and can update the sysconfig file instead of silently changin semantics of this variable

this is a real dodgy variable