Added the option of running chkboot with an update argument for when cha...

Just repeating my commit message: Added the option of running chkboot with an update argument for when changes are made on purpose; this updates the boot partition checksums without generating the alert file when it runs into the changes you made. This will remove the need to run it twice in these situations as well as restrict the log to only unexpected changes. There's also a help argument to show the syntax now that command line operations are possible, and I updated the initcpio script to use the update option to fix the fact that it was generating an alert each time it was legitimately run.