"Imported" name spaces (#5361)

"Imported" name spaces (#5361)

* Fixes for #5355:
- let's import SPL/extension classes and then just use them without name spaces
  like we do it with our own classes/interfaces, too.
- need to add namespace \ (global)

Signed-off-by: Roland Häder <roland@mxchange.org>
* Removed leading slashes from "import" lines.

Signed-off-by: Roland Häder <roland@mxchange.org>
* Completed:
- "import" other classes, then use them

Signed-off-by: Roland Häder <roland@mxchange.org>