Added require_order to Getopt::Long configuration

This makes it possible to execute cf-sketch commands with options from
the command line. For example, previously this:

$ cf-sketch.pl list -v

Would interpret the -v as the verbose flag for cf-sketch and not for
'list'. Adding require_order makes the cf-sketch option processing stop
when it encounters the first non-option argument, which gives us the
correct behavior.
Changed runfile name to cf-sketch-runfile.cf

This makes it match the file and hooks that are already included in
CFEngine, from the previous version of Design Center.
Print descriptions and default values, if any, in the output of info -v
Force install so that install also updates sketches, and remove source and target parameters, which are now optional.
Moved some user-prompting functions to Util.pm for general use.
Sketchify command

The sketchify command allows to interactively generate a sketch from an
existing policy file:

sketchify FILE.cf

And then follow the prompts. If needed, it automatically inserts the
namespace declaration and the runenv/environment parameters in the
generated file. It also generates a skeleton README.md file.
Merge pull request #351 from zzamboni/feature/sketchify

Implement "sketchify" command, to automatically create sketches from existing policy files.