Add new function 'conf.create' to conf utility, to allow for
creation-only of variables. If a key already exists, the variable is not
assigned. This allows the user to run the target 'configure' and not
fear that his/her changes are overwritten on the next 'configure' or
'build' run.
Update all targets that use 'conf' to use the .create function instead
of the .update function. The .update function is to only be used when
the explicit need of overriding previous setting is present.
Update log to be of a more useful and readable format.
Add lite spm.sh script, to replace bootstrapper script in the future.
Update README with information about the included spm.sh script.
Update target 'clone' to ensure a return value of something other than
nil.
Update spm.sh to latest revision to include all previous paklib changes.