Added a minimal CMake-ified shapelib (1.3.0).
Removed shapelib dependency.

A minimal shapelib is now part of the repo. This means shapelib stuff
is always available. Just include "shape/shapefil.h" and link to "shp".
Merge pull request #276 from bilke/shapelib

Remove shapelib dependency
Better disabling off warnings in ThirdParty/.
CMake SYSTEM includes are now also treated by Clang.
Compiles with VTK 6, not tested yet.
Search only for required vtk libs.
NetCDF from VTK is always used.
Removed OGS_LIBS_DIR-stuff, VTK is required for the gui.
Partly reverted last commit.
First attemp to link to locally built vtk.
Works on Mac.

Implementation from http://stackoverflow.com/a/17473508/80480
Works on Windows too.
Added vtk dependencies for the Gui.
Typo.
Switched local VTK to static libs and added a patch for a known VTK bug.

Bug fix: http://review.source.kitware.com/11956
Cleanup.
Build VTK with one core on travis.

Checks for the environment variable $CI.
Removed vtk from command line config.
Added CMake option OGS_SYSTEM_VTK_ONLY to prevent building Vtk locally.