Do not add a // slash if the URL doesn't contain a host

 - Add compliance with parse_url() with accepts url's of the format schema:path
 - Allow to parse and write object identifier uri's using as HttpUrl objects.
re #184 : Fix problem configuring a singleton identifier through the bootstrapper
re #187 : Properly clean output buffers.

If the php is setup to use output compression the zlib.output_compression buffer will be started by php and the starting level will be 1. This buffer cannot be cleaned, value stays 1 and we end up in a loop.