Integration of hierarchicah householder reduction trees

The goal of this merge request is to integrate through the libhqr (naming under discussion) the hierarchical householder trees for QR/LQ factorization, and open the pathe to SVD/EVD reduction to band integration, as they are presented in the following papers:

• Jack Dongarra, Mathieu Faverge, Thomas Hérault, Mathias Jacquelin, Julien Langou, et al.. Hierarchical QR factorization algorithms for multi-core clusters. Parallel Computing, Elsevier, 2013, 39 (4-5), pp.212-232. <10.1016/j.parco.2013.01.003>. https://hal.inria.fr/hal-00809770

• Mathieu Faverge, Julien Langou, Yves Robert, Jack Dongarra. Bidiagonalization and R-Bidiagonalization: Parallel Tiled Algorithms, Critical Paths and Distributed-Memory Implementation. IPDPS'17 - 31st IEEE International Parallel and Distributed Processing Symposium , May 2017, Orlando, United States. 2017, http://ipdps.org/. https://hal.inria.fr/hal-01484113

Files that have been added to the repository:

• Compute directory
  • pzgeqrf_param
  • pzunmqr_param
  • pzungqr_param
  • pzgelqf_param
  • pzunmql_param
  • pzunglq_param
  • geqrs_param driver
  • gelqs_param driver
  • gels_param driver
• Testing gels
  • gels_hqr
  • gels_systolic as a second step
  • Add list of ctest to test any default configuration
• Timing
  • time_zgeqrf_hqr
  • time_zgeqrf_hqr_tile
• Add the libhqr as a submodule
• Check builds with
  • Quark
  • StarPU