Allow resetting coverage collection during execution

[SimonKagstrom]

It could sometimes be useful to "reset" coverage collection during execution, e.g., to compare the state before and after some command has been executed.

This could be implemented via a pipe, so that restarting can be done via

echo "binary-name=hejsan" > /tmp/kcov/configuration.pipe

which would change the name of the binary and reset all breakpoints. The configuration changing interface can be used to propagate restarting.