Optimize linestring rendering via automatically assigned detail level values.

Review Request #123239 - Created April 3, 2015 and updated - Latest diff uploaded

Torsten Rahn
beschow, nienhueser, stanciu, tgridel

Allow for automatically assigning detail values to the nodes inside a linestring.
This mechanism is used for PN2 parsing in this patch.
Taking the detail level into account this approach improves geometry layer performance by 20% on my i7 based machine.
This patch also fixes the "backwards" semantical meaning of ViewportParams::resolve()
In the next step this optimization could also be applied during KML and OSM parsing.

Tested manually using the Atlas map, Plain map and Political map without apparent regressions. "make test" runs fine.
Checked the geometry layer values by starting Marble with --runtimeTrace. On average the msec values are about 20% lower on my machine (and I hope that improvement is even better on slower CPUs).
Ideas for unit tests regarding this patch are welcome. ;-)