Fix crash in tile fetcher when no engine is set.

The engine is stored in a QPointer. The pointer must be checked for
validity before use.

Change-Id: I07eaf9276511273735f000ce0eb9cdf2fe130df3
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Nokia plug-in URL and tiler API updates

Updated URLs for places and map tiler to current ones. Added URL
management for additional hosts for hybrid, terrain and satellite maps.
Added new languages and map types available in the new tiler API.

Bug fixes for code evaluating copyrights text to show. Now only
copyrights related to viewed maps are shown and each name is shown only
once.

Updated drawing of copyright information to show HERE logo and
copyrights text side by side. This is to avoid having logo jumping
up and down.

Change-Id: Ide18a95335c4299c8219c4dbcfb0cc60b43d46c3
Reviewed-by: Aaron McCarthy <mccarthy.aaron@gmail.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Merge pull request #26 from agunnarsson/master

Update Nokia map tile integration