add getfields function to PHPDoc

I wrote a getfields function for phpdoc while at dev camp but it wouldn't run on the server because it was looking for a civicrm.settings.php file (presumably the same issue where you can't generate DAO without a valid civicrm.settings.php even though it wouldn't seem required).

So, the problem is to get the function to run on the server when phpdoc is run

Michal started looking at it but it didn't get finished. I think it would be good to get this sorted as soon possible because we had a few people interested in helping with documentation & if we do this they can go through the API adding (e.g)

{@getfields activity}

to add the getfields version of accepted fields (getfields is like $dao->fields but is manually 'improved' on various API)