formatResults() now works with nested dicts.

The db.util.formatResults() can now format nested dictionaries to XML.
The other formats and tests are still missing.
Added tests for the XML formatting.
Added tests for JSON formatting.

They are already passing. No changes are needed.
Setting HTTP content-tpye for xml response.

Also changed the docstring for the formatResults function.
Changes to the XHTML output.

It now also works with lists of dictionaries. It still works with the
previously returned proxy results. In the case of a list of
dictionaries, the order of the keys, will represent the table headers,
will be alphabetically.

Also changes the normalize_whitespace() helper function to a generic xml
whitespace normalization function.

Added two short XHTML output tests.
Added XHTML output tests.

Checks that missing fields are dealt with.
XHTML output now correctly handles missing fields.
Added two tests for XHTML output.

A tabular view is not quite suited for deeper data structures so this
should not be of much use but at least it works.
Adding util test to __init__
Merge pull request #6 from krischer/master

More functionality for seishub.core.db.util.formatResults()