ADD: added more SPARQL domains.
FIX: ci_string//1 now works with strings (SWI7 compatibility).
FIX: ci_code//1 wrong variable instantiation.
CHANGED: skip retrieval of revisions, which breaks datahub.io.
ADDED: case-insensitivity of MIME type detection (XML and HTML files are case-insensitive for much of their grammar).
O: use of dcg_done//0  so we only have to parse the top few lines of a file (i.o. all lines).
DEB: added debug statements.
ADDED: choose between breadth-first and depth-first search (used to be only breadth-first).
ADDED: extended SPARQL domains.
CHANGED: no longer use library persistency for storing SPARQL endpoints (this seemed to prohibit multiple Prolog instances?).
NEW: dcg_done//0 when the rest of the code list is irrelevant.