They run for about 30 minutes each.

Started building VTK 8.0.1 packages but this not finished.

Small fixes

Ccache versions

Minimum version: 3.2

Disable optimization -O3 and the non-precise divisions.

The explicit default dtor makes the intel compiler 2017 unhappy
and it is not needed; the base class Element has an explicit
virtual dtor.

[CMake] Remove external projects

Possible values: missing (default), all, never, list of lib names

Examples:

cmake . -DOGS_CONAN_BUILD="Eigen3;Boost" -> Builds Eigen and Boost locally
cmake . -DOGS_CONAN_BUILD=all            -> Builds all libs locally

This basically reimplements all functionality we had with ExternalProject.

My Boost fix was integrated in 1.64.0 only.

Added Conan remote conan-community where the package is hosted.

The latter was reported N. Grunwald and should be fixed with the added
fPIC option in the VTK Conan package.

This makes sure that CMAKE_BUILD_TYPE variable is set which is
required by Conan.

Set OGS_USE_CONAN=ON to enable this. Once enabled there is no
conan install .. call necessary anymore.

You can select individual libraries to be used from the system, e.g.:

cmake -DOGS_USE_CONAN=ON -DOGS_LIB_VTK=System ..

This lets Conan install all third-party libraries except of VTK.

Fixes Eigen finding.

Local installation of libraries can be done with Conan.