This function returns the content of a document as an object of type
hw_api_content. The parameter array
contains the required elements 'objectidentifier' and the optional
element 'mode'. The mode can be one of the constants
HW_API_CONTENT_ALLLINKS,
HW_API_CONTENT_REACHABLELINKS or
HW_API_CONTENT_PLAIN.
HW_API_CONTENT_ALLLINKS means to insert all
anchors even if the destination is not reachable.
HW_API_CONTENT_REACHABLELINKS tells
hw_api_content() to insert only reachable links and
HW_API_CONTENT_PLAIN will lead to
document without any links.