This function checks out an object or a whole hiearchie
of objects. The parameters array contains the required
element 'objectIdentifier' and the optional element
'version', 'mode' and 'objectQuery'. 'mode' can be one of the
following values:
Checks out an object. The object must be a
document.
If the object to check out is a collection, all
children will be checked out recursively if they are
documents. Trying to check out a collection would
result in an error.
See also hwapi_checkin().