Moves files and directories:
1) src/lib => src/lib/marble
2) src/*marble-qt related* => src/apps/marble-qt
   src/*marble (KDE) related* => src/apps/marble-kde
   src/qt-components/marble-touch => src/apps/marble-touch

1) is a preparation to align the structure of installed headers with
the structure of the library sources, so that we can build tools and
examples in the same go and detect API changes early.
2) results in a much more tidy src/ and more intuitive location of the
sources of the respective applications.

REVIEW: 112114