CHOP-959: Introduce and use settings vars for some cmd_line switches.

The cmd_line.xml entries:
analyzeperformance
crashonstartup
debugsession
disablecrashlogger
logmetrics
logperformance
noquicktime
replaysession
all specify map-to settings.xml variables -- none of which existed! Introduce
such variables. Instead of detecting the presence of a particular switch in
the command-line parser, use the value of its corresponding settings variable.