Add support for specifying individual named targets on command-line.
Add support for specifying individual named targets on command-line.

Can now add '@target1,target2' after cake-script to build only those
specific targets rather than building the default target for the script.

Also added -l/--list-targets option that will print out the list of
named targets and the targets those names map to for the build scripts
you specify on the command-line.

lewissbaker/cake,lewissbaker/cake,lewissbaker/cake,lewissbaker/cake