Use OTEAPI to separate between download and parse strategies

[jesper-friis]

DLite storage plugins does not separate between download and parse strategies. Instead of implement this separation in DLite, use OTEAPI. In order to support this, we should change the signature of dlite_instance_load_url() and dlite_instance_save_url() to

dlite_instance_load_url(const char *parser, const char *url);

and

dlite_instance_save_url(const char *parser, const char *url, DLiteInstance *inst);

The parser argument should be used to select storage plugin, including OTEAPI parse strategy. The scheme of the URL is used by OTEAPI to select download strategy. If the URL does not contain a scheme, "file://" is implied.

The option and fragment parts of the URL may be used to provide options and instance id (UUID) to the parser.