Function to simplify making FHIR RESTful requests
requestType - The type of request
base - the base URI for the FHIR server
resourceType - the type of resource you're looking for
id - the id for the resource
resource - the resource itself, if appropriate
headers any headers that you want included in the request, these can
include authorization headers, although they may be overwritten if you
pass in a client as well
vid - the version id of the resource
client - if there's a specific client that you're going to be using
parameters - any extra parameters
count - The maximum number of search results on a page, excluding related
resources included by _include or _revinclude or OperationOutcomes. The
server is not bound to return the number requested, but cannot return more
since - Only include resource versions that were created at or after the
given instant in time
at - Only include resource versions that were current at some point
during the time period specified in the date time value
reference - Only include resource versions that are referenced in
the specified list
