mklive: added -v kerver option

[catvec]

#59

Added the -v option which lets users specify the kernel version to install onto the ISO. The option takes the name of the Linux package they would like to install.

Works by hijacking _linux_series variable and replacing it with the user's custom Linux package. Additionally adds the user specified Linux package onto the end of the PACKAGE_LIST variable so it is installed into the ISO.

I did some dumb git things on my end, just easier to close the old PR and open this one

[catvec]

Just tested by building an ISO with -v linux5.0, booted successfully from a USB with the ISO burnt.