HTTP authorization and other bug fixes.

- Fixed HTTP authorization.
- Fixed so that fields are properly cleared when loading fields from new
layers in the same session.
- Added specific warning message upon HTTP 401:Unauthorized response.
- Fixed so that no layer is selected automatically unless stated in the
configuration file.
- Fixed so that geometry text is not added as character data in XML.
- Fixed un-caught exception when loading configuration file with invalid
lines.