Please fix nepomuk-core buildsystem

[Albert Astals Cid]

I find it quite annoying that it tells me

-- Soprano version 2.7.5 is too old. Please install 2.7.56 or newer


and then tells me

-----------------------------------------------------------------------------
-- The following external packages were located on your system.
-- This installation will have the extra features provided by these packages.
-----------------------------------------------------------------------------
   * Soprano - Soprano is the Qt-based RDF storage and parsing solution

-----------------------------------------------------------------------------
-- Congratulations! All external packages have been found.
-----------------------------------------------------------------------------

If i get a "Congratulations!" message I expect that it will build.

Cheers,
  Albert