Added new MultiFetch define an some details

Hi Alessandro,

I've a new pull request for you. The changes are:
* moved defines & classes into extra files
* add a no_cert_check parameter for untrusted https connections
* refactored fetch & authfetch into one new define fetch. The new fetch should be compatible - but can you review this?
* added some specs
* add a multifetch in order to get multiple files from one baseurl.

Last but not least I changed the spec_helper to reflect my module directory structure. Maybe your spech helper has a parameter to adjust my modulepath? So I can use your unchanged spec_helper ...?

Best regards,
Michael