Enhance golo golo command to support folders and specific module

--files parse folders to load golo files
--module is added to specify a Module name for the main function

this command is valid
$ golo golo --files samples/ --module hello.World
Hello World!
$

And
- shell completion updated with --module
- documentation for this enhancement
- some samples have a new module name (to avoid duplication in classpath)
Enhance golo diagnose command to support directories

this command is valid
$ golo diagnose samples/
$
Enhance golo doc command to support directories

this command is valid
$ golo doc samples/
$
Add --usage to Golo script

this option --usage print the help for a command

this command is valid
$ golo --usage run
Runs compiled Golo code
Usage: run [options] Program arguments
  Options:
        --classpath
       Classpath elements (.jar and directories)
       Default: []
  *     --module
       The Golo module with a main function
$

and when a command fail, only the help of this command is print
Merge pull request #181 from rlespinasse/wip/gologolo-folders

Enhance some golo commands