- CMake 3.12.4
- Conan 1.18.0

Update servers for 17.10 were not available anymore.

Conan packages for gcc-6 are build on Ubuntu 17.10. VTK uses getrandom
which is implemented differently depending glibc version, thus the VTK
package for GCC 6 is incompatible to Ubuntu 16.04.

See also
https://www.opengeosys.org/docs/devguide/troubleshooting/conan/#something-went-wrong-during-building

Web site is build be Netlify.

6.2 is the minimum tested compiler by our CI (on envinf1).
6.5 is the default gcc 6 in Ubuntu 16.04 when using the ubuntu-toolchain-r/test PPA.

See

- https://include-what-you-use.org
- https://blog.kitware.com/static-checks-with-cmake-cdash-iwyu-clang-tidy-lwyu-cpplint-and-cppcheck/

Added gcc.full Docker image definition.