add a new benchmark "BHE Array" to the web content.

ProcessLib/HeatConduction/Tests.cmake

Tests/Data/Parabolic/T/2D_BHE_array/bhe2d.gml

Tests/Data/Parabolic/T/2D_BHE_array/bhe2d.prj

Tests/Data/Parabolic/T/2D_BHE_array/bhe2d.vtu

...tandard_solution_bhe2d_pcs_0_ts_840_t_72576000.000000.vtu

...docs/benchmarks/heatconduction/BHE_array_benchmark.pandoc

...s/heatconduction/BHE_array_benchmark_figures/figure_1.png

...s/heatconduction/BHE_array_benchmark_figures/figure_2.png

...s/heatconduction/BHE_array_benchmark_figures/figure_3.png

...s/heatconduction/BHE_array_benchmark_figures/figure_4.png

...s/heatconduction/BHE_array_benchmark_figures/figure_5.png

.../benchmarks/heatconduction/bhe_array_analytical_solver.py

...nt/docs/benchmarks/heatconduction/bhe_array_benchmark.bib