Add a crash handler part 2

HI Matt,

In the spirit of following the push frequently philosophy, I am presenting this pull request to you. This completes the second part of two of the crash handler.

This part utilizes vmcore-dmesg, part of kexec-tools, to extract the dmesg buffer from the vmcore memory dump. When booting from runlevel 3, the contents of the dmesg buffer are saved on the test results partition of the LuvOS media. Also, functionality is added to inform the user of all the actions taken.

Additionally, the kexec-tools recipe is modified to explicitly select the 2.0.7 version of kexec-tools. This provides tighter control (and reproducible build across hosts) of the version used. The version is important as previous versions will not be able to parse the dmesg buffer correctly due to changes in the Linux kernel.

Thanks and BR,
Ricardo