textproc/kreport: Shift dependencies after 116eb4a7d098

With the addition of the MARBLE option in 116eb4a7d098, several Qt
dependencies can be conditionalized based on whether astro/marble was
built with the WEBENGINE option enabled. This should enable building
on platforms that cannot build qt5-webengine.

Disable Marble detection the cannonical way to avoid CMake warnings.

Add LICENSE info (LGPL2+), remove outdated CONFLICTS line, and clean
up whitespace issues.